The Book of Suckling
17/6. Chapter:
Becoming Mahram is established by Five Breastfeedings
Sahih Muslim
وَحَدَّثَنَاهُ مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا عَبْدُ الْوَهَّابِ، قَالَ سَمِعْتُ يَحْيَى بْنَ سَعِيدٍ، قَالَ أَخْبَرَتْنِي عَمْرَةُ، أَنَّهَا سَمِعَتْ عَائِشَةَ، تَقُولُ . بِمِثْلِهِ .
Ahadith like this is transmitted by 'A'isha through another chain of narrators.
Reference : Sahih Muslim 1452cIn-book reference : Book 17, Hadith 32USC-MSA web (English) reference : Book 8, Hadith 3423