It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: Whoever has intercourse with his menstruating wife, or approaches his wife from behind, or goes to a fortune-teller and affirms what he says, he has disassociated himself from the religion which Allah Almighty has revealed to Muhammad (peace and blessings be upon him).
Hadith Referenceالفتح الربانی / كتاب الحيض والإستحاضة والنفاس / 934