Hisnul Muslim 192

Before sexual intercourse

بِسْمِاللَّهِ، اللَّهُمَّ جَنِّبْنَا الشَّيْطَانَ، وَجَنِّبِ الشَّيْطَانَ مَا رَزَقْـتَنَا

Bismillaah. Allaahumma jannibnash-Shaytaana, wa jannibish-Shaytaana maa razaqtanaa.

With the Name of Allah. O Allah, keep the Devil away from us and keep the Devil away from that which You provide for us.