Musnad Ahmad 4087

It was narrated from Abu Moosa al-Hilali, from his father, that A man was on a journey and his wife gave birth, but her milk would not come. So he started to suckle and spit out the milk, but some of it entered his stomach. He came to Abu Moosa, who said: She has become haram for you. He went to Ibn Mas’ood and asked him, and he said: The Messenger of Allah (ﷺ) said: "Breastfeeding does not make a person a mahram except that which causes the flesh and bones to grow.”