Zayd bin Aslam (may Allah have mercy on him) said: Abd al-Malik bin Marwan would send for Umm al-Darda' (may Allah be pleased with her), and she would spend the night with his wives, and he would ask her about matters. He said: One night he got up and called his servant; she was slow, so he cursed her. She said: Do not curse, for Sayyiduna Abu al-Darda' (may Allah be pleased with him) told me that he heard the Prophet (peace and blessings be upon him) say: "Those who curse will not be witnesses or intercessors on the Day of Resurrection."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 20792