Sunan an-Nasa'i, Hadith 3300 ⓘ
It was narrated from 'Aishah that the Prophet said: "What becomes unlawful (for marriage) through birth becomes unlawful through breast-feeding."
أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا يَحْيَى، قَالَ أَنْبَأَنَا مَالِكٌ، قَالَ حَدَّثَنِي عَبْدُ اللَّهِ بْنُ دِينَارٍ، عَنْ سُلَيْمَانَ بْنِ يَسَارٍ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " مَا حَرَّمَتْهُ الْوِلاَدَةُ حَرَّمَهُ الرَّضَاعُ " .
also referenced under: Book 26, Hadith 105 (In-Book) & Volume 4, Book 26, Hadith 3302 (DarusSalam)