It is narrated from Hazrat Abu Musa (may Allah be pleased with him) that I heard the Noble Prophet (peace and blessings be upon him) say: Whoever does a good deed and feels happy about it, and commits a sin and feels sad about it, then he is a believer.
Hadith Referenceمسند احمد / تتمہ مُسْنَدِ الْكُوفِيِّينَ / 19565
Hadith Gradingحکم دارالسلام:صحيح لغيره، وهذا إسناد ضعيف لانقطاعه، المطلب لا يعرف له سماع من الصحابة