Abu Darda narrated
that Rasool Allah said, “Should I not tell you of such a thing which are the best and purest deeds in the court of your Lord, high in ranks (darajat), better for you then spending gold and silver (in Allah’s path), and better than slaying the neck of the enemy during war? The Sahaba said, “Yes, Oh Rasool Allah! .” He said, “It is Zikr of Allah.” (Tirmizi)