Narrated Thâbit bin Ad-Dahhak, who was one of the companions who gave the Bai'a (pledge) to the Prophet (ﷺ) underneath the tree (Al-Hudaibîya): Allâh's Messenger (ﷺ) said, "Whoever swears by a religion other than Islâm (i.e., if somebody swears by saying that he is a non-Muslim e.g., a Jew or a Christian, etc.) in case he is telling a lie, he is really so if his oath is false, and a person is not bound to fulfill a vow about a thing which he does not possess. (1) And whoever commits suicide with anything in this world, he will be tortured with that very thing on the Day of Resurrection; and whoever curses a believer, then it (his sin) will be as if he murdered him; and whoever accuses a believer of Kufr (disbelief), then it is as if he killed him. [8:73-O.B]