The Book of Marriage
26/54. Chapter:
Al-Ghilah (Intercourse With A Breast-feeding Woman)
Sunan an-Nasai
أَخْبَرَنَا عُبَيْدُ اللَّهِ، وَإِسْحَاقُ بْنُ مَنْصُورٍ، عَنْ عَبْدِ الرَّحْمَنِ، عَنْ مَالِكٍ، عَنْ أَبِي الأَسْوَدِ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، أَنَّ جُدَامَةَ بِنْتَ وَهْبٍ، حَدَّثَتْهَا أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " لَقَدْ هَمَمْتُ أَنْ أَنْهَى عَنِ الْغِيلَةِ حَتَّى ذَكَرْتُ أَنَّ فَارِسَ وَالرُّومَ يَصْنَعُهُ " . وَقَالَ إِسْحَاقُ " يَصْنَعُونَهُ فَلاَ يَضُرُّ أَوْلاَدَهُمْ " .
It was narrated from 'Aishah that Judamah bint Wahb told her that the Messenger of Allah said: "I was thinking of forbidding Ghilah until I remembered that it is done by the Persians and Romans" -(one of the narrators) Ishaq said: "(They) do that -and it does not harm their children."
Reference : Sunan an-Nasa'i 3326In-book reference : Book 26, Hadith 131English translation : Vol. 4, Book 26, Hadith 3328