Musnad Ahmad 1153:1632

'Abd al-Razzaq narrated to us, he said: Ibn Jurayj informed us, he said: Ibn Shihab informed us, 'Urwah ibn al-Zubayr informed me, from 'Aishah, that Abu Hudhayfah adopted Salim—and he was a freedman of a woman from the Ansar—just as the Prophet, peace and blessings of Allah be upon him, adopted Zayd. Whoever adopted a man in the Pre-Islamic Period (Jahiliyyah), the people would call him his son, and he would inherit from his inheritance, until Allah, the Almighty and Majestic, revealed: "Call them by [the names of] their fathers; it is more just in the sight of Allah. But if you do not know their fathers - then they are [your] brothers in religion and those entrusted to you" [Al-Ahzab: 5]. So they were returned to their fathers. Whoever did not have a known father, he was a freedman and a brother in religion. Then Sahlah came and said: "O Messenger of Allah, we used to consider Salim a son; he would stay with me and with Abu Hudhayfah, and he would see me unveiled, and Allah, the Almighty and Majestic, has revealed regarding them what you know." He said: "Breastfeed him five times, and he will be in the position of her son through breastfeeding."