Riyad as-SalihinChapter 1Hadith 15
Full Sharh — Riyad as-Salihin 15
وعن أبي ذر رضي الله عنه قال: قال لي رسول الله صلى الله عليه وسلم : "لا تحقرن من المعروف شيئاً، ولو أن تلقى أخاك بوجه طلق" ((رواه مسلم)).
English Translation
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.".
Source
Riyad as-Salihin(رياض الصالحين)
The Book of Good Manners
Hadith Number
15