Abu Ad-Darda reported: The Messenger of Allah, peace and blessings be upon him, said, “Those who curse others will not be intercessors or witnesses on the Day of Resurrection.”

Source: Sahih Muslim 2595

Grade: Sahih (authentic) according to Muslim

عن أبي الدرداء قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لَا يَكُونُ اللَّعَّانُونَ شُفَعَاءَ وَلَا شُهَدَاءَ يَوْمَ الْقِيَامَةِ

2595 صحيح مسلم كِتَاب الْبِرِّ وَالصِّلَةِ وَالْآدَابِ بَاب النَّهْيِ عَنْ لَعْنِ الدَّوَابِّ وَغَيْرِهَا

http://dailyhadith.abuaminaelias.com/2010/09/14/those-who-curse-will-not-intercede-or-witness-on-the-day-of-judgment/