Therefore are they before the throne of God, and serve him day and night in his temple: and he that sitteth on the throne shall dwell among them. Therefore - Because they are washed in the blood of the Lamb, are they before the throne - admitted to the immediate presence, of God.
And serve him day and night - Without ceasing; being filled with the spirit of prayer, faith, love, and obedience.
Shall dwell among them - He lives in his own Church, and in the heart of every true believer.