Abu Darda on Curses: Do not curse anyone, not befitting believers

Hakim ibn Jabir reported: Abu Darda, may Allah be pleased with him, was lying down between his companions and he had a cloth over his face. A priest passed by him and they were amazed at how fat he was. They said, “O Allah, curse him! How big is he! How fat is he!” Abu Darda lifted the cloth from his face and he said, “Who have you cursed so disdainfully?” They said, “A priest passed by us.” Abu Darda said, “Do not curse anyone. It is not befitting for one in the habit of cursing to be among the truthful to Allah on the Day of Resurrection.”

Source: al-Zuhd wal-Raqā’iq 668

عَنْ حَكِيمِ بْنِ جَابِرٍ قَالَ كَانَ أَبُو الدَّرْدَاءِ رضي الله عنه مُضْطَجِعًا بَيْنَ أَصْحَابِهِ وَثَوْبُهُ عَلَى وَجْهِهِ إِذْ مَرَّ بِهِمْ قُسٌّ فَأَعْجَبَهُمْ سِمَنُهُ فَقَالُوا اللَّهُمَّ الْعَنْهُ مَا أَعْظَمَهُ وَمَا أَسْمَنَهُ فَكَشَفَ الثَّوْبَ عَنْ وَجْهِهِ فَقَالَ مَنْ ذَا الَّذِي لَعَنْتُمْ آنِفًا قَالُوا قُسًّا مَرَّ بِنَا قَالَ لا تَلْعَنُوا أَحَدًا فَإِنَّهُ لا يَنْبَغِي لِلَّعَّانِ أَنْ يَكُونَ عِنْدَ اللَّهِ يَوْمَ الْقِيَامَةِ صِدِّيقًا

668 الزهد والرقائق لابن المبارك