Volume 1, Book 4, Number 143:
Narrated Ibn ‘Abbas:
The Prophet said, “If anyone of you on having sexual relations with his wife said (and he must say
it before starting) ‘In the name of Allah. O Allah! Protect us from Satan and also protect what you be –
stow upon us (i.e. the coming offspring) from Satan, and if it is destined that they should have a child
then, Satan will never be able to harm that offspring.”