Sahih Muslim #2637
Sahih (Authentic)
Good Character
الْبِرُّ حُسْنُ الْخُلُقِ وَالإِثْمُ مَا حَاكَ فِي صَدْرِكَ وَكَرِهْتَ أَنْ يَطَّلِعَ عَلَيْهِ النَّاسُ
The Prophet (ﷺ) said: 'Righteousness is good character, and sin is that which wavers in your heart and which you do not want people to know about.'
Chain of Narration (Isnad)
Narrated An-Nawwas bin Sam'an