It is narrated from Sayyidah Aisha (may Allah be pleased with her) that Sayyiduna Abu Bakr (may Allah be pleased with him) cursed one of his slaves, so the Prophet (peace and blessings be upon him) said: "Abu Bakr! Does a Siddiq also curse? Never, by the Lord of the Ka'bah." The Prophet (peace and blessings be upon him) repeated this two or three times. Sayyiduna Abu Bakr (may Allah be pleased with him) freed several of his slaves that day, then presented himself before the Prophet (peace and blessings be upon him) and said: I will never curse again.
Hadith Referenceالادب المفرد / كتاب / 319
Hadith Gradingالألبانی:صحيح
Hadith Takhrij«صحيح : الترغيب : 286/3 - أخرجه البيهقي فى شعب الإيمان : 5154»