Sahih Muslim
The Book of Destiny (Kitab-ul-Qadr)
Book Number: 033 / Hadith Number: 6396
Hadhaifa b. Usaid Ghifari, a Companion of Allah's Messenger (may peace be upon him), 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.