Narrated Ibn `Abbas:
The Prophet (Peace and Blessings of Allah be upon him) said,
“If anyone of you, when having sexual relation with his wife, say:
بِسْمِ اللَّهِ اللَّهُمَّ جَنِّبْنَا الشَّيْطَانَ، وَجَنِّبِ
الشَّيْطَانَ مَا رَزَقْتَنَا ‘
In the name of Allah. O Allah! Protect us from Satan and prevent Satan from approaching our offspring you are going to give us,’ and if he begets a child (as a result of that relation) Satan will not harm it.”
Bukhari 3271.