Nahj al-Balāgha
Hadith 1632سَعِ النَّاسَ بِوَجْهِكَ وَمَجْلِسِكَ وَحُكْمِكَ، وإِيَّاكَ وَالْغَضَبَ فَإِنَّهُ طَيْرَةٌ مِنَ الشَّيْطَانِ.
Meet people with a broad face, allow them free audience and pass generous orders. Avoid anger because it is a augury of Satan.