From Ibn 'Abbas (radiyallahu 'anhu):
The Prophet (alayhi salat wa salam) stated that Allah Most High said:

"Indeed, the salat is only accepted from one who humbles himself in it before My Immensity, who is not overbearing towards My creatures, who does not persist in rebellion towards Me, who spends his days invoking (dhikr) Me, who shows mercy to the bereft, the widow, the traveler, and the afflicted. The spiritual light of such a one is as brilliant as the sun’s light! I preserve him with My Might, and charge My angels to protect him, and grant him light at the place of darkness, and knowledge at the place of ignorance, and his similarity to My other creation is as the Firdaws (the highest level of Paradise) to the remainder of Paradise"

Recorded by Hafiz Abu Bakr Bazzar in his Musnad