It is narrated from Urwah that the Prophet ﷺ instructed the wife of Abu Hudhaifah (Sahlah) to breastfeed Salim five times, and he would become her mahram through her milk. She did so, and she considered Salim as her son.
Hadith Referenceمسند الإمام الشافعي / كتاب النكاح / 1189