Abdullah bin Abbas reported,

The Messenger of Allah ﷺ was asked about ghilah, the practice of a husband having intercourse with his wife while she is nursing. He replied, "If it were harmful to anyone, it would have harmed the Persians and the Romans."

Azami 6383

Sahih

عن عبد الله بن عباس

أن رسول الله ﷺ سئل عن الغيل فقال: لو كان ضارا أحدا ضر فارس والروم.

الأعظمي 6383صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Marriage
Chapter
Rights and duties of the Muslim woman, and good treatment of her
Section
Ghilah
Numbering
Jami al-Kamil 6383 (2nd edition)
Azami 6383