It is narrated from Sayyiduna Thabit bin al-Dahhak al-Ansari (may Allah be pleased with him) that he said: The Messenger of Allah (peace and blessings be upon him) said: "Cursing a believer is like killing him; and whoever accuses a believing man or a believing woman of disbelief, it is like killing him; and whoever swears by a religion other than Islam, he is as he said; and whoever kills himself with something will be punished with it on the Day of Resurrection; and a servant has no vow in what he does not own."
Hadith Referenceالمعجم الكبير للطبراني / باب الثاء / 1317