Intercourse during breastfeeding

[Quran 6:150] Say, "Bring your witnesses who would testify that GOD has prohibited this or that." If they testify, do not testify with them. Nor shall you follow the opinions of those who reject our revelations, and those who disbelieve in the Hereafter, and those who stray away from their Lord.

(١٥٠) قُلْ هَلُمَّ شُهَدَاءَكُمُ الَّذِينَ يَشْهَدُونَ أَنَّ اللَّهَ حَرَّمَ هَٰذَا فَإِنْ شَهِدُوا فَلَا تَشْهَدْ مَعَهُمْ وَلَا تَتَّبِعْ أَهْوَاءَ الَّذِينَ كَذَّبُوا بِآيَاتِنَا وَالَّذِينَ لَا يُؤْمِنُونَ بِالْآخِرَةِ وَهُمْ بِرَبِّهِمْ يَعْدِلُونَ

وَحَدَّثَنَا خَلَفُ بْنُ هِشَامٍ، حَدَّثَنَا مَالِكُ بْنُ أَنَسٍ، ح وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، - وَاللَّفْظُ لَهُ - قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ مُحَمَّدِ بْنِ عَبْدِ الرَّحْمَنِ بْنِ نَوْفَلٍ عَنْ عُرْوَةَ عَنْ عَائِشَةَ عَنْ جُدَامَةَ بِنْتِ وَهْبٍ الأَسَدِيَّةِ أَنَّهَا سَمِعَتْ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏ "‏ لَقَدْ هَمَمْتُ أَنْ أَنْهَى عَنِ الْغِيلَةِ حَتَّى ذَكَرْتُ أَنَّ الرُّومَ وَفَارِسَ يَصْنَعُونَ ذَلِكَ فَلاَ يَضُرُّ أَوْلاَدَهُمْ ‏"‏ ‏.‏ قَالَ مُسْلِمٌ وَأَمَّا خَلَفٌ فَقَالَ عَنْ جُذَامَةَ الأَسَدِيَّةِ ‏.‏ وَالصَّحِيحُ مَا قَالَهُ يَحْيَى بِالدَّالِ ‏.‏

Judaima daughter of Wahb al-Asadiyya (Allah be pleased with her) reported that she heard Allah's Messenger (ﷺ) assaying: I was intending to prohibit intercourse with a suckling woman until I considered that the Romans and the Persians do it without any injury being caused to their children thereby. (Imam Muslim said: Khalaf reported it from Judamat al-'Asadiyya, but the correct wording is what has been stated by Yahya.)