Sunan Ibn Majah 1919

It was narrated from Ibn `Abbas:that the Prophet said: “When anyone of you has intercourse with his wife, let him say: Allahumma jannibnish-Shaitana wa jannibish-Shaitana ma razaqtani (O Allah, keep Satan away from me and keep Satan away from that with which You bless me).' Then if they have a child, Allah will never allow Satan to gain control over him or he will never harm him.”