Bismillah Walhamdulillah Was Salaatu Was Salaam ‘ala Rasulillah
Narrated Ibn Abbas (Radi-Allahu ‘anhu):
The Prophet (Sallallahu ‘Alaihi Wa Sallam) 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.”
Bukhari Vol. 7 : No. 94