Kitāb al-Muʾmin
Hadith 181181 - وعن أبي عبد الله عليه السلام أنه قال: لا تستخف بأخيك المؤمن فيرحمه الله عز وجل عند استخفافك، ويغير ما بك.
181. It has been narrated that Abu 'Abd Allah (a.s) said: Do not belittle your brother-in-faith lest Allah [M.G] should show mercy to him while you are belittling him and your circumstances should change for worse.