Hadithcore
Mishkat al-Masabih, 3173

Umm Salama reported God’s Messenger as saying, “The only suckling which makes marriage unlawful is that which is taken from, the breast and enters the bowels, and is taken before the time of weaning.” Tirmidhi transmitted it.

وَعَنْ أُمِّ سَلَمَةَ قَالَتْ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «لَا يُحَرِّمُ مِنَ الرِّضَاعِ إِلَّا مَا فَتَقَ الْأَمْعَاءَ فِي الثَّدْيِ وَكَانَ قبل الْفِطَام» . رَوَاهُ التِّرْمِذِيّ

References1 variant
In-Book Reference
Book 13, Hadith 91