Abu Huraira رضي الله عنه (May Allah be pleased with him) said: The Prophet صلى الله عليه وسلم (Peace be upon him) was asked to curse the Polytheists(Mushrikeen). He said, "I have not been sent to curse people but as a mercy to all mankind.

[Sahi Muslim, Hadith no. 6613]

Abu Huraira رضي الله عنه (May Allah be pleased with him) reported Allah's Messenger صلى الله عليه وسلم (Peace be upon him) as saying: It does not seem proper for Siddiq that he should be an invoker of curse.

[Sahi Muslim, Hadith no. 6608]

Prophet صلى الله عليه وسلم (Peach be upon him) said: A believer does not taunt, curse, abuse or talk indecently.

[Sunan Tirmidhi, Hadith no. 1977, Authentic]