What is incumbent upon one who doubts whether he swore by Allah or by divorce?

Whoever is certain that he swore an oath, but doubts whether he swore by Allah or by divorce, then he must offer expiation for an oath if he breaks it. This is because the original state is the continuation of the marriage, and divorce is doubtful, and marriage is not dissolved by doubt. If one swears by divorce, and does not intend divorce, it is an oath for which expiation is due upon breaking it, according to the preponderant opinion. And doubt often arises when one intended to urge or prevent something, but did not intend divorce, and in such a case, only the expiation for an oath is required upon breaking it. It is not permissible to swear by divorce, as the Prophet, peace and blessings be upon him, said: «Whoever swears an oath, let him swear by Allah or remain silent», and «Whoever swears by anything other than Allah has committed shirk (associating partners with Allah)».