The Messenger of Allah ﷺ said, "It does not befit a believer to be one who frequently curses."
قال رسول الله ﷺ: لا ينبغي للمؤمن أن يكون لعانا.
No references are available.
Tirmidhi (2019) narrated it, as did Bukhari in Adab al-Mufrad (309), and Hakim graded it sahih (1/47), all of them through the route of Kathir bin Zayd, from Salim bin Abdullah, from his father Abdullah bin Umar, who said, and then he mentioned it. Its chain is hasan because of Kathir bin Zayd Madani, for his narrations are hasan. Tirmidhi also graded it hasan, saying, "This is a hasan gharib hadith."