Musnad Ahmad 1907

It was narrated from Ibn "Abbas, who attributed it to the Prophet (ﷺ): “If one of you says, when he has intercourse with his wife, "In the Name of Allah, O Allah, keep the Shaitan away from me and keep the Shaitan away from what You bless us with," if it is decreed that they should have a child as a result of that, the Shaitan will never harm him."