In the Hadith of Ibn Abbaas, The Prophet salallahu alayhi wasallam said:
“If anyone of you, when having sexual intercourse with his wife, says:
بِسمِ اللهِ اللهُمَّ جَنَّبنا الشَّيطَانَ و جَنَّبِ الشَّيطَانَ ما رَزَقتَنا Bismillah, Allahumma jannibnish-Shaitan wa jannibish-Shaitana ma razaqtana
In the Name of Allaah, O Allaah, keep Shaitaan away from us and keep the Shaitaan away from that which You provide for us.
and if it is destined that they should have a child, then Satan will never be able to harm him.” (Sahih Bukhari Volume 7, Book 62, Number 94)