Sahih Bukhari Volume 007, Book 062, Hadith Number 025.
Narrated By 'Aisha : Abu Hudhaifa bin 'Utba bin Rabi'a bin Abdi Shams who had witnessed the battle of Badr along with the Prophet adopted Salim as his son, to whom he married his niece, Hind bint Al-Walid bin 'Utba bin Rabi'a; and Salim was the freed slave of an Ansar woman, just as the Prophet had adopted Zaid as his son. It was the custom in the Pre-lslamic Period that if somebody adopted a boy, the people would call him the son of the adoptive father and he would be the latter's heir. But when Allah revealed the Divine Verses: 'Call them by (the names of) their fathers... your freed-slaves,' (33.5) the adopted persons were called by their fathers' names. The one whose father was not known, would be regarded as a Maula and your brother in religion. Later on Sahla bint Suhail bin 'Amr Al-Quraishi Al-'Amiri and she was the wife of Abu- Hudhaifa bin 'Utba came to the Prophet and said, "O Allah's Apostle! We used to consider Salim as our (adopted) son, and now Allah has revealed what you know (regarding adopted sons)." The sub-narrator then mentioned the rest of the narration.