رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 694
The Book of Good Manners
Excellence of Meeting with a Smiling Countenance and Politeness in Speech
وَعَنْ أَبِي ذَرٍّ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ لِي رَسُولُ اللَّهِ صَلَّى اللَّه عَلَيْهِ وَسَلَّمَ : لاَ تَحْقِرَنَّ مِنَ الْمَعْرُوفِ شَيْئًا، وَلَوْ أَنْ تَلْقَى أَخَاكَ بِوَجْهٍ طَلْقٍ ((رَوَاهُ مُسْلِم)).
Abu Dharr (May Allah be pleased with him) reported: Messenger of Allah (ﷺ) said, "Do not disdain a good deed, (no matter how small it may seem) even if it is your meeting with your (Muslim) brother with a cheerful face." [Muslim].
Riyad as-Salihin, 694