The importance of Dhikr (Remembrance) -
Yahya related to me from Malik that Ziyad ibn Abi Ziyad said that Abu'd-Darda had said, "Shall I not tell you the best of your deeds, and those that give you the highest rank, and those that are the purest with your King, and are better for you than giving gold and silver, and better for you than meeting your enemy and striking their necks?" They said, "Of course." He said, "Remembrance (dhikr) of Allah ta ala." (Imam Malik: Muwatta Book 15 No 15.7.24)
Malik related to me from Nuaym ibn Abdullah ibn al-Mujmir from AIi ibn Yahya az-Zuraqi from his father that Rifaa ibn Rafi said, "One day we were praying behind the Messenger of Allah, (SAW), when the Messenger of Allah, (SAW), raised his head from ruku and said, 'Allah hears the one who praises Him' (Sami Allahu liman hamidah). A man behind him said, 'Our Lord, praise belongs to you - blessed, pure and abundant praise' (Rabbana wa laka'l hamd kathiran tayiban mubarakan fihi). When the Messenger of Allah, (SAW), had finished, he said, 'Who was it who spoke just now?' The man said, 'I did, Messenger of Allah,' and the Messenger of Allah, (SAW), said, 'I saw more than thirty angels rushing to it to see which one of them would record it first.' "
(Imam Malik: Muwatta Book 15 No 15.7.25)