Sanctification is the act or process of acquiring sanctity, of being made or becoming holy. "Sanctity" is an ancient concept widespread among religions. It is a gift given through the power of God to a person or thing which is then considered sacred or set apart in an official capacity within the religion, in general anything from a temple, to vessels, to days of the week, to a human believer who willingly accepts this gift can be sanctified. To sanctify is to literally "set apart for particular use in a special purpose or work and to make holy or sacred." Etymologically, "sanctify" derives from the Latin verb sanctificare which in turn derives from sanctus "holy" and facere "to make".
In the various branches of Christianity sanctification usually refers to a person becoming holy, with the details differing in different branches.
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 and Evangelical 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. 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 their 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.
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, the founder of Lutheranism, 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. 
John Wesley, the founder of Methodism, taught what is known as entire sanctification in the holiness movement churches, such as the Church of the Nazarene, the Salvation Army, or Christian perfection in "mainstream" Methodist denominations, such as the United Methodist Church, the Methodist Church of Great Britain. 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 explained in depth in the essay, "Entire Sanctification" by Adam Clarke as well as, later, in Articles of Religion in the Book of Discipline of the Methodist Church. "Initial salvation" is sometimes 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."
United Methodists believe that sanctifying grace draws one toward the gift of Christian perfection, which Wesley 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".
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.
Other Christian denominations and movements
Beliefs about sanctification vary amongst the Christian denominations and movements, influenced by various Christian movements. These beliefs differ from each other on: whether sanctification is a definitive experience or process, when the process/experience takes place, and if entire sanctification is possible in this life.
Influenced by the Holiness movement some Pentecostal churches, such as the Church of God in Christ and the Apostolic Faith Church, believe that sanctification is a definitive act of God’s grace and spiritual experience whereby we are made holy subsequent to salvation and prior to the baptism of the Holy Spirit. Reformed Churches are amongst denominations that teach about definitive sanctification at the time of conversion, and believers are required to "do good works" which are "… all sanctified by (God’s) grace". Similarly, non-Wesleyan Pentecostals such as Assemblies of God teach about definitive sanctification at the time of conversion and progressive sanctification after conversion. Converted believers are expected to "make every effort to live a holy life… Even though Christians may not attain absolute perfection in this life." The event of entire sanctification occurs when Christ comes back and gives us glorified bodies.
Higher Life movement and Brunstad Christian Church believe that sinless perfection is attainable in Christian life. Higher Life movement teaches that even though believers still have an inclination to sin after conversion, they must constantly rely on the Holy Spirit to struggle against this tendency, and therefore can attain sinless perfection in this life. Further, the movement proclaims that "the secret of complete victory is faith: simply believing that Jesus has done and is doing all". On the contrary, Brunstad Christian Church teaches that because Jesus, as a man, was tempted in all points as other human beings, yet never committed sin, he opened a way back to God, and therefore those who want to be disciples can follow on that same way. They proclaim that this means a Christian does not only receive the forgiveness of sins, but can also conquer all sinful tendencies in their own human nature.
Church of Jesus Christ of Latter-day Saints
In the Church of Jesus Christ of Latter-day Saints sanctification is a process and gift from God which makes every willing member holy, according to their works, as Saints of God. 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 live a holy life to truly be considered Holy. In the most basic sense, to be Sanctified you must First, Love thy God with all thy heart, might, mind, and soul; And love thy neighbor as thy self. In the scriptural canon of The Church of Jesus Christ of Latter-day Saints, one reference to sanctification is given in the following Book of Mormon scripture: Helaman 3:35, "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." Dallin H. Oaks, an LDS General authority and member of the Quorum of the Twelve Apostles, can more fully expand on the meaning of sanctity and other matters of great importance.
- The Mitzvah of sanctifying the Kohen
- Divine Grace
- Imparted righteousness
- Justification (theology)
- Means of Grace
- Social Gospel
- Oxford English Dictionary, 2nd ed.Sanctify: to make (a person) holy, to purify or free from sin
- 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. http://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 â€" A Calvinist Viewpoint | Calvinism | Sanctification â€" 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
- 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 Karkkainen: "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
- The United Methodist Church: The Articles of Religion of the Methodist Church - Of Sanctification
- "Distinctive Wesleyan Emphases (Page 2)". Archives.umc.org. 2006-11-06. Retrieved 2012-08-04.
- Catholic Encyclopedia: Sanctity
- Church of God in Christ. "What we believe". Retrieved February 9, 2011.
- Apostolic Faith Church. "Our Faith - Doctrines". Retrieved May 24, 2011.
- Mike Sullivan. "Five Views on Sanctification: An In-Depth Analysis".
- Christian Reformed Church. "The Belgic Confession".
- Assemblies of God USA. "Sanctification & Holiness".
- J. Robertson McQuilkin, "The Keswick Perspective," In Five Views on Sanctification (Grand Rapids: Academic Books, 1987), p. 156.
- Charles G. Trumbull, Victory in Christ (Fort Washington: Christian Literature Crusade, 1959), 84, 48.
- Brunstad Christian Church. "Our Faith".
- "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
- Sanctification: heat and glow from the fire, Forward in Christ
- The dictionary definition of sanctification at Wiktionary
- Sanctification: A Biblical Perspective