Sahih Muslim Book 32, Hadith Number 6286.

Chapter : He upon whom Allah’s Apostle (may peace be upon him) invoked curse whereas he in fact did not deserve it, it would be a source of reward and mercy for him.

This hadith has been reported on the authority of A’mash with the same chain of transmitters and the hadith transmitted on the authority of ‘Isa (the words are): “He had a private meeting with them and hurled malediction upon them and cursed them and sent them out.”