What is the meaning of "kādhiban" (lying/a liar) in the two hadiths: "Whoever swears by a religion other than Islam, lying deliberately, he is as he said," and "Whoever swears, saying: 'I am disavowed from Islam,' then if he was lying, he is as he said, and if he was truthful, he will not return to Islam safely"? And does it mean lying about the desire for disbelief or about the matter sworn upon? And what is the meaning of "ṣādiqan" (truthful/truthfully) in the second hadith? And does "he is as he said" mean immediate disbelief upon committing the sworn-upon act, even if he did not intend disbelief, or does he not disbelieve, as reported from Ibn Taymiyyah, if his intention was aversion and repulsion? And what is the ruling on someone who swore by disbelief, intending and desiring it, then repented and regretted? Does he disbelieve if he commits the sworn-upon act after that? And what is the ruling on swearing in the past tense, such as saying: "He is a disbeliever if he did such-and-such," while he is lying?

This answer summarizes issues related to swearing by a religion other than Islam as follows:

First: It is stated in the noble Hadith that "Whoever swears by a religion other than Islam, lying deliberately, then he is as he said," and "Whoever swears and says, 'Indeed, I am innocent of Islam,' if he is lying, then he is as he said, and if he is truthful, he will not return to Islam sound."

Truthfulness and falsehood in this context may have two meanings: 1. Regarding news about the past: As if one says, "If he did such and such, then he is a Jew," and he had indeed done it, then he is lying in his oath. 2. Regarding a condition for the future: As if one says, "If he does such and such, then he is a Jew." Here, lying means not fulfilling what he swore upon, and truthfulness means doing it. Some scholars believe that truthfulness and falsehood relate to venerating the disbelieving religion; if he swore while venerating it, then he is truthful (meaning he has fallen into what he said), and if he swore without venerating it, then he is lying.

Second: One does not disbelieve in the case of swearing about the past unless one intended to venerate the disbelieving religion. One does not disbelieve in the case of swearing about the future merely by the occurrence of the action, but rather disbelieves only if one intended, by their condition, to exit Islam (an intention of disbelief).

The imams have agreed that if one says, "He is a Jew or a Christian if he does such and such," and then does it, he does not disbelieve. Rather, he owes an expiation for an oath according to some, and nothing according to others.

Third: If a person swears by disbelief intending disbelief, then repents and feels remorse, he does not disbelieve if he performs the sworn-upon action after his repentance; because disbelief is related to the intention and acceptance of disbelief, and repentance removes this intention and acceptance.

Fourth: If one swears by disbelief concerning a past matter, lying, then he does not disbelieve unless he intended to venerate disbelief. This is the more apparent view. Some Hanafis believe that he disbelieves immediately if he believes that he will disbelieve by doing so.