Hadith 3881
Narrated Asma, daughter of Yazid ibn as-Sakan,: I heard the Messenger of Allah ﷺ as saying: Do not kill your children secretly, for the milk, with which a child is suckled while his mother is pregnant, overtakes the horseman and throws him from his horse.
Hadith 3882
Judamat al-Asadiyyah said that she heard the Messenger of Allah ﷺ Say: I intended to prohibit suckling during pregnancy (ghailah), but I considered the Greeks and the Persians and saw that they practiced it, without any injury being caused to their children thereby. Malik said: Ghailah means that a man has intercourse with a women while she is suckling a child.