كتاب الجامع
16  
The Comprehensive Book
Abu Dharr (RAA) narrated that the Messenger of Allah (ﷺ) said:
“Do not consider any act of goodness as being insignificant even if it is meeting your brother with a cheerful face.” Related by Muslim.
وَعَنْ أَبِي ذَرٍّ ‏- رضى الله عنه ‏- قَالَ: قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ لَا تَحْقِرَنَّ مِنْ اَلْمَعْرُوفِ شَيْئًا, وَلَوْ أَنْ تَلْقَى أَخَاكَ بِوَجْهٍ طَلْقٍ } 1


‏1 ‏- صحيح.‏ رواه مسلم (2626)‏.‏

Sunnah.com reference : Book 16, Hadith 27
English translation : Book 16, Hadith 1506
Arabic reference : Book 16, Hadith 1463