ENOfficial
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."
Source: sunnah.com
Other translations
Arabic
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 .
sunnah.com