“No prohibition results from suckling except for what penetrates the intestines while on the breast before weaning.” (Using translation from Tirmidhī 1152)
قَالَ رَسُولُ اللهِ ﷺ «لَا يُحَرِّمُ مِنَ الرَّضَاعِ إِلَّا مَا فَتَقَ الْأَمْعَاءَ فِي الثَّدْيِ وَكَانَ قَبْلَ الْفِطَامِ»