What is the ruling on a husband having intercourse with his wife if a divorce has occurred due to his swearing by divorce upon her if she did such and such, knowing that he has offered an expiation for an oath, believing it to be obligatory, then he came to know that the majority of jurists do not obligate an expiation for a divorce oath?

The fatwa (definition) on the issue of swearing by divorce is based on the opinion of the majority of scholars that divorce occurs when one breaks the oath. However, some scholars, like Ibn Taymiyyah, are of the view that an oath not intended to effect divorce falls under the ruling of swearing by Allah, requiring an expiation for the oath and not resulting in divorce. There is no harm in acting upon the opinion of some differing scholars as long as the questioner is confident in its validity and is not merely following his desires. If you act upon the opinion of Ibn Taymiyyah and those who agreed with him, and you offer expiation for your oath, then there is no harm. As for the opinion that divorce occurs, some scholars hold that resuming conjugal relations with the wife before the expiration of her waiting period constitutes a رجعة (revocation of divorce).