(51) باب الْقَدْرِ الَّذِي يُحَرِّمُ مِنَ الرَّضَاعَةِ .
It was narrated that Masruq said:
"Aishah said: 'The Messenger of Allah entered upon me and there was a man sitting with me. He got upset about that, and I saw the anger in his face.' I said: "O Messenger of Allah, he is my brother through breast-feeding." He said: "Be careful who you count as your brothers" --or: "be careful who you count as your brothers through breast-feeding"-- "for the breast-feeding (which makes marriage prohibited) is from hunger."
Reference: Sunan an-Nasa'i 3312
In-book reference: Book 26, Hadith 117
English translation: Vol. 4, Book 26, Hadith 3314