Inna Lillahi wa inna ilayhi raji'un
Inna lillahi wa inna ilayhi raji'un (Arabic: إِنَّا لِلّهِ وَإِنَّـا إِلَيْهِ رَاجِعونَ) is a part of a verse from the Qur'an which translates to "We belong to Allah and to Him we shall return."[n 1] The phrase is recited by Muslims when a person experiences a tragedy in life, especially upon hearing news that a person has died. The phrase may also be recited in situations that involve risk of any sort.
Muslims believe in the oneness of Allah, and that only Allah gives and takes away, sometimes to test humankind. Hence, Muslims submit to Allah and are grateful and thankful to Him for whatever they receive.
Abu Sinan said: "I buried my son Sinan and Abu Talhah Al-Khawlani was sitting on the rim of the grave. When I wanted to leave he took me by my hand and said: 'Shall I not inform you of some good news O Abu Sinan!' I said: 'Of course.' He said: 'Ad-Dahhak bin Abdur-Rahman bin Arzab narrated to me, from Abu Musa Al-Ash'ari: "The Messenger of Allah said: 'When a child of the servant(of Allah) died, Allah says to the angels: "Have you taken the fruits of his work." They reply: "Yes." So He says: "What did My servant say?" They reply: "He praised you and mentioned that to You is the return." So Allah says: "Build a house in Paradise for My servant, and name it 'the house of praise.'" [Jami` at-Tirmidhi 1021, Book 10, Hadith 57] 
A brief grammatical overview of the sentence is presented below:
ʾInnā: means Indeed we or verily we. "ʾInnā" is a contraction of ʾinna-nā. The first part means verily, the last part we. As the Arabic language tends to simplification, it is written as ʾinnā, with only one nūn and shadda for stress.
Li-llāhi: "Li" is a ḥarfu jarr (preposition) meaning "to" or "is for", and is used as a type of possessive case. "A laka ʾakhun" (where "la" is the same as "li") means “is for you a brother?” or “do you have a brother?” So here, "lillāhi" means "belong to Allāh" or "are for Allāh" (it is also because of the "li" that "Allāh" takes kasra).
Wa: Wa means "and".
ʾInnā: See above.
Ilay-hi: In two parts, this means "toward Him". "ʾIlay" is actually a form of "ʾila" (a preposition), which means "to". A grammatically similar phrase is "dhahabtu ʾila masjidin" ("I went to a mosque"). "Hi" is actually "hu", the third-person possessive pronoun (meaning his), and takes kasra because of "ʾila".
Rājiʿūn: This is a form of rajaʿa, "return" (the "ʿ" represents the letter ʿain, which is voiced with a tightened throat). "Rājiʿ" is a noun/adjective form, meaning "a person who is returning." The suffix "–ūn" plural (so that it refers to three or more people). "Rājiʿūn" thus basically means "returners", or better "the returning ones".
Taken together, the phrase can be translated as "We indeed belong to Allah, and we indeed toward Him are returning."
- "al-Baqarah 2:156". Retrieved 25 December 2013.
- "Islam Question and Answer - The believer's attitude towards calamities". IslamQA. Retrieved 30 April 2011.
- "When one is struck by calamity (trouble)". iSunnah. Retrieved 30 April 2011.
- "Hadith - The Book on Janaiz (Funerals) - Jami` at-Tirmidhi - Sunnah.com - Sayings and Teachings of Prophet Muhammad (صلى الله عليه و سلم)".
- "Word-by-Word Quran - Verse (2:156)". Kais Dukes. Retrieved 30 April 2011.