What is the ruling on one who swore an oath of divorce regarding something, not remembering whether it is with him or not, and claimed it was not with him while it was?

If one swears an oath about something while doubting it or having a weak assumption, then breaking the oath and repenting from the lie are necessary. However, if one swears an oath believing firmly in their truthfulness, then there is no breaking of the oath upon them, nor is a divorce or expiation required, even if reality turns out to be contrary to what they swore. It is worth noting that swearing by Allah is the prescribed way, whereas swearing by divorce is among the oaths of the dissolute.