Jami` at-Tirmidhi, Hadith 2005 ⓘ
Abu Wahb narrated that : 'Abdullah bin Al-Mubarak explained good character, and then he said: "It is a smiling face, doing one's best in good, and refraining from harm."
حَدَّثَنَا أَحْمَدُ بْنُ عَبْدَةَ الضَّبِّيُّ، حَدَّثَنَا أَبُو وَهْبٍ، عَنْ عَبْدِ اللَّهِ بْنِ الْمُبَارَكِ، أَنَّهُ وَصَفَ حُسْنَ الْخُلُقِ فَقَالَ هُوَ بَسْطُ الْوَجْهِ وَبَذْلُ الْمَعْرُوفِ وَكَفُّ الأَذَى .
also referenced under: Book 27, Hadith 111 (In-Book) & Volume 4, Book 25, Hadith 2005 (DarusSalam)