Sunan Ibn Majah, Chapter: The Chapters on Etiquette

that the Prophet(saw) said: "Shall I not tell you of the best of your deeds, the most pleasing to your Sovereign, those that raise you most in status, that are better than your gold and silver, or meeting your enemy (in battle) and you strike their necks and they strike your necks?" They said: " What is that, O Messenger of Allah?" He said: "Remembering Allah (Dhikr)."