Volume 7, Book 62, Number 94:
Narrated Ibn Abbas:
The Prophet said, “If anyone of you, when having sexual intercourse with his wife, says: Bismillah,
Allahumma jannibni-Sh-Shaitan wa jannib-ish-Shaitan ma razaqtana, and if it is destined that they
should have a child, then Satan will never be able to harm him.”