Anas ibn Malik reported: The Prophet, peace and blessings be upon him, would not insult others, he would not use profanity, and he would not curse others. If he wanted to criticize one of us, he would say, “What is the matter with him? His forehead be dusted!”
Source: Ṣaḥīḥ al-Bukhārī 6031
Grade: Sahih (authentic) according to Al-Bukhari
عَنْ أَنَسِ بْنِ مَالِكٍ رَضِيَ اللَّهُ عَنْهُ قَالَ لَمْ يَكُنْ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ سَبَّابًا وَلَا فَحَّاشًا وَلَا لَعَّانًا كَانَ يَقُولُ لِأَحَدِنَا عِنْدَ الْمَعْتِبَةِ مَا لَهُ تَرِبَ جَبِينُهُ
6031 صحيح البخاري كتاب الأدب باب لم يكن النبي صلى الله عليه وسلم فاحشا ولا متفحشا