(27) Chapters on Righteousness And Maintaining Good Relations With Relatives
كتاب البر والصلة عن رسول الله صلى الله عليه وسلم
(62) Chapter: What Has Been Related About Good Character
(62) باب مَا جَاءَ فِي حُسْنِ الْخُلُقِ
Jami` at-Tirmidhi 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 ‏.‏
Grade :  Sahih (Darussalam)
Reference : Jami` at-Tirmidhi 2005
In-book reference : Book 27, Hadith 111
English translation : Vol. 4, Book 1, Hadith 2005