Musnad Ahmad 1153:2296

Ya'qub narrated to us, he said: My father narrated to us, from Ibn Ishaq, he said: Al-Zuhri narrated to me, from 'Urwah, from 'Aishah, she said: Sahlah bint Suhayl came to the Messenger of Allah, may Allah bless him and grant him peace, and said to him: "O Prophet of Allah, Salim was among us as you know; we used to consider him a son, and he would enter upon me as he wished, and we did not feel shy before him. But when Allah revealed concerning him and those like him what He revealed, I noticed the expression on Abu Hudhayfah's face when he saw him entering upon me." He said: "Breastfeed him ten times, then he may enter upon you as he wishes, for he is your son." 'Aishah used to view this as general for the Muslims, while the other wives of the Prophet, may Allah bless him and grant him peace, viewed it as having been specific to Salim, the freed slave of Abu Hudhayfah, regarding whom Sahlah had mentioned the situation as a concession for him.