Sanctification is the act or process of acquiring sanctity, of being made or becoming holy.
In rabbinic Judaism sanctification means sanctifying God's name by works of mercy and martyrdom, while desecration of God's name means committing sin. This is based on the Jewish concept of God, who's holiness is pure goodness and is transmissible by sanctifying people and things.
The Catholic Church upholds the doctrine of sanctification, teaching that:
Sanctifying grace is that grace which confers on our souls a new life, that is, sharing in the life of God. Our reconciliation with God, which the redemption of Christ has merited for us, finds its accomplishments in sanctifying grace. Through this most precious gift we participate in the divine life; we have the right to be called children of God. This grace is the source of all our supernatural merits and bestows upon us the right of eternal glory.
According to the Catholic Encyclopedia "sanctity" differs for God, individual, and corporate body. For God, it is God's unique absolute moral perfection. For the individual, it is a close union with God and the resulting moral perfection. It is essentially of God, by a divine gift. For a society, it is the ability to produce and secure holiness in its members, who display a real, not merely nominal, holiness. The Church's holiness is beyond human power, beyond natural power.
Sanctity is regulated by established conventional standards.
Orthodox Christianity teaches the doctrine of theosis, whereby humans take on divine properties. A key scripture supporting this is 2 Peter 1:4. In the 4th century, Athanasius taught that God became Man that Man might become God. Essentially, Man does not become divine, but in Christ can partake of divine nature. This Church's version of salvation restores God's image in man. One such theme is release from mortality caused by desires of the world.
Martin Luther, taught in his Large Catechism that Sanctification is only caused by the Holy Spirit through the powerful Word of God. The Holy Spirit uses churches to gather Christians together for the teaching and preaching of the Word of God.
Sanctification is the Holy Spirit's work of making us holy. When the Holy Spirit creates faith in us, he renews in us the image of God so that through his power we produce good works. These good works are not meritorious but show the faith in our hearts (Ephesians 2:8-10, James 2:18). Sanctification flows from justification. It is an on-going process which will not be complete or reach perfection in this life.
Luther also viewed the Ten Commandments as means by which the Holy Spirit sanctifies.
"Thus we have the Ten Commandments, a commend of divine doctrine, as to what we are to do in order that our whole life may be pleasing to God, and the true fountain and channel from and in which everything must arise and flow that is to be a good work, so that outside of the Ten Commandments no work or thing can be good or pleasing to God, however great or precious it be in the eyes of the world...whoever does attain to them is a heavenly, angelic man, far above all holiness of the world. Only occupy yourself with them, and try your best, apply all power and ability, and you will find so much to do that you will neither seek nor esteem any other work or holiness."
A 2002 Anglican publishing house book states that “there is no explicit teaching on sanctification in the Anglican formularies”. A glossary of the Episcopal Church (USA) gives some teaching: “Anglican formularies have tended to speak of sanctification as the process of God's work within us by means of which we grow into the fullness of the redeemed life.” Outside official formularies sanctification has been an issue in the Anglican Communion since its inception.
The 16th century Anglican Theologian Richard Hooker (1554-1600) distinguished between the “righteousness of justification” that is imputed by God and the “righteousness of sanctification” that comprises the works one does as an “inevitable” result of being justified.
A 19th century Church of England work agreed with Jeremy Taylor that justification and sanctification are “inseparable”. However, they are not the same thing. Justification is “found in Christ’s work alone”. “Sanctification is the work of the Holy Spirit in us, and is a progressive work.”
Calvinist theologians interpret sanctification as the process of being made holy only through the merits and justification of Jesus Christ through the work of the Holy Spirit that are then reflected in man. Sanctification cannot be attained by any works-based process, but only through the works and power of the divine. When a man is unregenerate, it is his essence that sins and does evil. But when a man is justified through Christ, it is no longer the man (in his essence) that sins, but the man is acting outside of his character. In other words, the man is not being himself, he is not being true to who he is.
In Wesleyan-Arminian theology, which is upheld by the Methodist Church as well as by Holiness Churches, "sanctification, the beginning of holiness, begins at the new birth". With the Grace of God, Methodists "do works of piety and mercy, and these works reflect the power of sanctification". Examples of these means of grace (works of piety and works of mercy) that aid with sanctification include frequent reception of the sacrament of Holy Communion (work of piety), and visiting the sick and those in prison (work of mercy). Wesleyan covenant theology also emphasizes that an important aspect of sanctification is the keeping of the moral law contained in the Ten Commandments. As such, in "sanctification one grows to be more like Christ." This process of sanctification that begins at the new birth (first work of grace) has its goal as Christian perfection, also known as entire sanctification (second work of grace), which John Wesley, the progenitor of the Methodist faith, described as a heart "habitually filled with the love of God and neighbor" and as "having the mind of Christ and walking as he walked". This is the doctrine that by the power of God's sanctifying grace and attention upon the means of grace may cleanse a Christian of the corrupting influence of original sin in this life. It is expounded upon in the Methodist Articles of Religion:
Sanctification is that renewal of our fallen nature by the Holy Ghost, received through faith in Jesus Christ, whose blood of atonement cleanseth from all sin; whereby we are not only delivered from the guilt of sin, but are washed from its pollution, saved from its power, and are enabled, through grace, to love God with all our hearts and to walk in his holy commandments blameless.
Justification is seen as an initial step of acknowledging God's holiness, with sanctification as, through the grace and power of God, entering into it. A key scripture is Hebrews 12:14: "Follow after...holiness, without which no one shall see the Lord." The Wesleyan Church (formerly known as the Wesleyan Methodist Church) states that sanctification has three components—initial, progressive, and entire:
We believe that sanctification is that work of the Holy Spirit by which the child of God is separated from sin unto God and is enabled to love God with all the heart and to walk in all His holy commandments blameless. Sanctification is initiated at the moment of justification and regeneration. From that moment there is a gradual or progressive sanctification as the believer walks with God and daily grows in grace and in a more perfect obedience to God. This prepares for the crisis of entire sanctification which is wrought instantaneously when believers present themselves as living sacrifices, holy and acceptable to God, through faith in Jesus Christ, being effected by the baptism with the Holy Spirit who cleanses the heart from all inbred sin. The crisis of entire sanctification perfects the believer in love and empowers that person for effective service. It is followed by lifelong growth in grace and the knowledge of our Lord and Savior, Jesus Christ. The life of holiness continues through faith in the sanctifying blood of Christ and evidences itself by loving obedience to God’s revealed will.
There are two Pentecostal positions on sanctification, entire sanctification and progressive sanctification. 
Entire sanctification as a second work of grace, is the position of Pentecostal denominations that originally had their roots in Wesleyan-Arminian theology, such as the International Pentecostal Holiness Church, Church of God (Cleveland), Christian and Missionary Alliance , and the International Church of the Foursquare Gospel. These denominations differ from the Methodist Churches (inclusive of the Holiness Movement) in that they teach the possibility of a third work of grace--glossolalia.
Progressive sanctification is the work of sanctification of the believer through grace and the decisions of the believer after the new birth.  This is the position of other Pentecostal denominations, such as the Assemblies of God. 
The Church of Jesus Christ of Latter-day Saints
In the Church of Jesus Christ of Latter-day Saints (LDS Church) sanctification is a process and gift from God which makes every willing member holy, according to their repentance and righteous efforts, through the Savior Jesus Christ's matchless grace.To become Sanctified, or Holy, one must do all that he can to live as Christ lived, according to the teachings of Christ. One must strive to live a holy life to truly be considered Holy. In the scriptural canon of the LDS Church, one reference to sanctification appears in Helaman 3:35, in the Book of Mormon:
Nevertheless they did fast and pray oft, and did wax stronger and stronger in their humility, and firmer and firmer in the faith of Christ, unto the filling their souls with joy and consolation, yea, even to the purifying and the sanctification of their hearts, which sanctification cometh because of their yielding their hearts unto God.
In Islam, sanctification is used to pray about saints, especially among Sufis, in whom it is common to say "that God sanctifies his secret" ("qaddasa Llahou Sirruhu"), and that the Saint is alive or dead. 
- Jewish Encyclopedia: Sanctification of the Name
- Jewish Encyclopedia: Holiness
- Justo L. González, Essential Theological Terms, Westminster John Knox Press, USA, 2005, p. 155
- Fitzgerald, Maurus (2011). Order of Malta Catholic Book of Prayers. Catholic Book Publishing Corp. p. 240.
- Catholic Encyclopedia: Sanctity Archived 2011-01-05 at the Wayback Machine
- Athanasius: "On the Incarnation", Crestwood: Saint Vladimir's Seminary Press, 1989. p.93
- Robert V. Rakestraw: "On Becoming God: An Evangelical Doctrine of Theosis," Journal of Evangelical Theological Society 40/2 (June 1997) 257-269
- Veli-Matti Kärkkäinen: "One With God: Salvation as Deification and Justification," Collegeville: Liturgical Press, 2004. p.18
- Lutheran Dogmaticians consider this the broad sense of sanctification. See Luther's Large Catechism, the Apostle's Creed, paragraph 53 and following
- WELS Topical Q&A: Sanctification and Justification, by Wisconsin Evangelical Lutheran Synod
- From Luther's Large Catechism, the Ten Commandments, paragraph 311 and following. For further reading of Lutherans on Sanctification, see Sanctification in Lutheran Theology by David P. Scaer, The Lutheran Doctrine Of Sanctification And Its Rivals by John F. Brug, Sanctification In The Lutheran Confessions by Lyle W. Lange, and Apostles’ Creed, Third Article - Of Sanctification: The Holy Ghost Works Through The Word by A. J. Kunde
- Granquist, Mark A. (2015). Scandinavian Pietists: Spiritual Writings from 19th-Century Norway, Denmark, Sweden, and Finland. Paulist Press. p. 13. ISBN 9781587684982.
- Owen C. Thomas, Ellen K. Wondra, Introduction to Theology, 3rd ed (Church Publishing, 2002), 222.
- Don S. Armentrout and Robert Boak Slocum, eds, An Episcopal Dictionary of the Church (Church Publishing, 2000), s. v. "Sanctification", 467. Online at http://www.episcopalchurch.org/library/glossary/sanctification-0
- Gibbs, Lee W. "Richard Hooker's Via Media Doctrine of Justification" in The Harvard Theological Review 74, no. 2 (1981): 211-220. https://www.jstor.org/stable/1509447 (accessed June 10, 2010).
- Ralph McMichael, ed, The Vocation of Anglican Theology: Sources and Essays (SCM, 2014), 214-215.
- An Explanation of the Articles of the Church of England, Part 1 (Church of England, 1843), 53. Online at https://books.google.com/books?id=yTJWAAAAcAAJ&source=gbs_navlinks_s
- Dane says:. "Sanctification - A Calvinist Viewpoint | Calvinism | Sanctification - A Calvinist Viewpoint". Learntheology.com. Retrieved 2012-08-04.
- Gerhard O. Forde, Donald L. Alexander, Sinclair B. Ferguson: "Christian spirituality: five views of sanctification", InterVarsity Press, 1988. p. 47-76
- Kettenring, Keith (15 September 2007). The Sanctification Connection. University Press of America. p. 29. ISBN 9780761837381.
- Abraham, William J.; Kirby, James E. (24 September 2009). The Oxford Handbook of Methodist Studies. Oxford University Press. p. 475. ISBN 9780191607431.
- Jr, Charles Yrigoyen (25 September 2014). T&T Clark Companion to Methodism. A&C Black. p. 259. ISBN 9780567290779.
- White, James W. (17 March 2014). Brief Christian Histories: Getting a Sense of Our Long Story. Wipf and Stock Publishers. p. 99. ISBN 9781556352430.
He espoused a "method" of study, prayer, and community by which persons might know "sanctification" before God. Wesley thought that the truly devout could "move on to perfection," an ends ethic idea. The Methodist Book of Discipline with "Rules for Methodist Societies" specified what the ways were: daily reading of the Bible, prayer, feeding the hungry, and visiting the sick and those in prison.
- Campbell, Ted A. (1 October 2011). Methodist Doctrine: The Essentials, 2nd Edition. Abingdon Press. pp. 40, 68–69. ISBN 9781426753473.
- Jones, Scott J. (1 September 2010). United Methodist Doctrine. Abingdon Press. p. 197. ISBN 9781426725593.
- Campbell, Ted A. (1 October 2011). Methodist Doctrine: The Essentials, 2nd Edition. Abingdon Press. p. 41. ISBN 9781426753473.
Methodist piety describes the goal of sanctification as entire sanctification or Christian perfection. If the notion of perfection is offensive, it is also biblical: Jesus taught us to "Be perfect, therefore as your heavenly Father is perfect" (Matthew 5:48). And to what perfection can human beings aspire? Methodists have always answered this by repeating the Great Commandment: "You shall love the Lord your God with all your heart, and with all your soul, and with all your mind" (Matthew 22:37; cf. Mark 12:30, Luke 10:27). Along with this, Methodists insist that Christian perfection also means the fulfillment of the second Commandment: love of our neighbor. Thus, Christian perfection or entire sanctification denotes primarily the perfection of our love for God and for our neighbor.
- "Distinctive Wesleyan Emphases (Page 2)". Archives.umc.org. 2006-11-06. Retrieved 2012-08-04.
- The United Methodist Church: The Articles of Religion of the Methodist Church - Of Sanctification
- "Articles of Religion: The Wesleyan Church". The Wesleyan Church. 2017. Retrieved 29 May 2018.
- Headley, Anthony J. (4 October 2013). "Getting It Right: Christian Perfection and Wesley's Purposeful List". Seedbed. Retrieved 29 May 2018.
- Roger E. Olson, The Westminster Handbook to Evangelical Theology, Westminster John Knox Press, USA, 2004, p. 319
- William Kostlevy, Historical Dictionary of the Holiness Movement, Scarecrow Press, USA, 2009, p. 148
- The West Tennessee Historical Society Papers - Issue 56. West Tennessee Historical Society. 2002. p. 41.
Seymour's holiness background suggests that Pentecostalism had roots in the holiness movement of the late nineteenth century. The holiness movement embraced the Wesleyan doctrine of "sanctification" or the second work of grace, subsequent to conversion. Pentecostalism added a third work of grace, called the baptism of the Holy Ghost, which is often accompanied by glossolalia.
- Roger E. Olson, The Westminster Handbook to Evangelical Theology, Westminster John Knox Press, USA 2004, p. 319
- Keith Kettenring, The Sanctification Connection: An Exploration of Human Participation in Spiritual Growth, University Press of America, USA, 2008, p. 29
- Cecil M. Robeck, Jr, Amos Yong, The Cambridge Companion to Pentecostalism, Cambridge University Press, UK, 2014, p. 76
- Mark Juergensmeyer, Wade Clark Roof, Encyclopedia of Global Religion, SAGE Publications, USA, 2011, p. 1116
- See D. Todd Christofferson, "Justification and Sanctification," Ensign, June 2006; C. Eric Ott, "Sanctification," Encyclopedia of Mormonism.
- "Helaman 3:35". The Church of Jesus Christ of Latter-day Saints. Intellectual Reserve, Inc. Retrieved 28 October 2012.
- Oaks, Dallin H. (November 2000), "The Challenge to Become", Ensign: 32
- Juan Eduardo Campo, Encyclopedia of Islam, Infobase Publishing, USA, 2009, p. 598