From Sahih Muslim (Hadith 6729):
Hadhaifa b. Usaid Ghifari, a Companion of Allah's Messenger (ﷺ), reported it directly from Allah's Messenger (may peace upon him). as he said:There is an angel who looks after the womb when Allah decides to create any- thing after more than forty nights are over; the rest of the hadith is the same
Reference: Muslim 6729