Musnad Ahmad 25:71

Sufyan narrated to us, from Mansur, from Salim, from Kurayb, from Ibn Abbas, who attributed it to the Prophet (peace and blessings of Allah be upon him): "If one of them, when he approaches his wife, says: 'In the name of Allah. O Allah, keep Satan away from me, and keep Satan away from what You have provided us,' and a child is decreed between them, Satan will never harm him."