Nawwas bin Sam'an (May Allah be pleased with him) reported:
I asked Messenger of Allah ﷺ about virtue and sin, and he said, "Virtue is noble behaviour, and sin is that which creates doubt and you do not like people to know about it."

[Muslim].

وعن النواس بن سمعان رضي الله عنه قال: سألت رسول الله ﷺ عن البر والإثم فقال: “البر حسن الخلق، والإثم: ما حاك في نفسك وكرهت أن يطلع عليه الناس” ((رواه مسلم)).