عن أبي أمامة رضي الله عنه أن رجلا قال يا رسول الله ما الإيمان قال إذا سرتك حسنتك وساءتك سيئتك فأنت مؤمن (مجمع الزوائد #286)

Hazrat Abu Umaamah (radhiyallahu ‘anhu) narrates that a Sahaabi (radhiyallahu ‘anhu) asked Rasulullah (sallallahu ‘alaihi wasallam), “What is (a sign of true) Imaan?” Rasulullah (sallallahu ‘alaihi wasallam) replied, “When your good deeds please you (on account of you fulfilling the command of Allah Ta‘ala), and your evil deeds cause you sadness (on account of you breaking the command of Allah Ta‘ala), then (it is a sign that) you are a (true) believer.”