Musnad Ahmad 31:661

And with this chain of narration, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The Lord, Mighty and Majestic is He, will say on the Day of Resurrection: 'The people of the gathering will know today who the people of nobility are.'" It was said: "And who are the people of nobility, O Messenger of Allah?" He said: "The circles of dhikr (remembrance of Allah) in the mosques."