What is the ruling on one who insists on swearing by other than Allah, while knowing that it is a hidden shirk, and what is the ruling on one who deems that permissible while knowing of its prohibition?

It is not permissible for a Muslim to deliberately swear by other than Allah, for swearing by other than Allah is shirk (polytheism). It is minor shirk and does not expel one from the fold of Islam unless the swearer intends to glorify the one sworn by, like glorifying Allah. In that case, it becomes major shirk that expels one from the fold of Islam. The Prophet, peace and blessings be upon him, forbade swearing by forefathers and others, and commanded swearing by Allah or remaining silent. This categorization of shirk is for the sake of extreme deterrence and strict prohibition. If a Muslim persists in swearing by other than Allah after knowing the prohibition, he is in grave danger, and he must repent. It is not permissible to imitate those who deemed it merely disliked or prohibited after knowing the authentic narrations. As for considering swearing by other than Allah permissible, one does not commit an act of disbelief by it unless its prohibition is unanimously agreed upon and its ruling has become clear among Muslims.