Muwatta Malik, Book 30, Hadith 10 (USC-MSA)

Yahya related to me from Malik that Ibrahim ibn Uqba asked Said ibn al-Musayyab about suckling. Said said, "All that occurs in the first two years, even if it is only a drop, makes haram. Whatever is after two years, is only food that is eaten." Ibrahim ibn Uqba said, ''Then I asked Urwa ibn az-Zubayr and he told me the same as what Said ibn al-Musayyab said."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ إِبْرَاهِيمَ بْنِ عُقْبَةَ، أَنَّهُ سَأَلَ سَعِيدَ بْنَ الْمُسَيَّبِ عَنِ الرَّضَاعَةِ، فَقَالَ سَعِيدٌ كُلُّ مَا كَانَ فِي الْحَوْلَيْنِ وَإِنْ كَانَتْ قَطْرَةً وَاحِدَةً فَهُوَ يُحَرِّمُ وَمَا كَانَ بَعْدَ الْحَوْلَيْنِ فَإِنَّمَا هُوَ طَعَامٌ يَأْكُلُهُ ‏.‏ قَالَ إِبْرَاهِيمُ بْنُ عُقْبَةَ ثُمَّ سَأَلْتُ عُرْوَةَ بْنَ الزُّبَيْرِ فَقَالَ مِثْلَ مَا قَالَ سَعِيدُ بْنُ الْمُسَيَّبِ ‏.‏

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also referenced under: Book 30, Hadith 1284 (In-Book)