CURSE:

ALLAH's Messenger has said: "Whe a man curses somebody, then that curse rises up to the sky, but finds the gates of the sky shut. Then it turn to the earth. Here also the gates are found shut. Therefore it wanders to the right and to the left, and if it does not find a proper place it goes to the man who was cursed. If he deserve it, well and good, otherwise it returns to the man who cursed."
--- (Abu Daud)