Sayyiduna Thabit bin Dhahak (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: Whoever swears a false oath by a religion other than Islam, it is as if he is as he said. (That is, if he says, "If I am lying, then I become a Jew," etc., then he becomes a Jew.) This hadith is from Ali bin Muhammad, and it also includes the addition that Sayyiduna Thabit bin Dhahak (may Allah be pleased with him) was among those Companions who pledged allegiance (Bay'at al-Ridwan) to the Prophet under the tree.