Sahih Muslim #2588
Sahih (Authentic)
Mercy
لاَ تَحْقِرَنَّ مِنَ الْمَعْرُوفِ شَيْئًا وَلَوْ أَنْ تَلْقَى أَخَاكَ بِوَجْهٍ طَلْقٍ
The Messenger of Allah (ﷺ) said: 'Do not despise any act of goodness, even meeting your brother with a cheerful face.'
Chain of Narration (Isnad)
Narrated Abu Huraira