It is narrated from Sayyiduna Thabit bin al-Dahhak (may Allah be pleased with him) that he said: The Messenger of Allah (peace and blessings be upon him) said: "There is no oath in disobedience to Allah, nor in what the son of Adam does not own; and whoever curses a Muslim, it is like killing him; and whoever calls a Muslim a disbeliever has himself become a disbeliever; and whoever deliberately swears falsely by a religion other than Islam, he is as he said; and whoever kills himself with something by which he dies, he is in Hell."
Hadith Referenceالمعجم الكبير للطبراني / باب الثاء / 1326