"The Church even now is the kingdom of Christ and the kingdom of heaven. Accordingly, even now His saints reign with Him, though otherwise than as they shall reign hereafter; and yet, though the tares grow in the Church along with the wheat, they do not reign with Him. For they reign with Him who do what the apostle says, 'If you are risen with Christ, mind the things which are above, where Christ sits at the right hand of God. Seek those things which are above, not the things which are on the earth'."

Source: The Works of Aurelius Augustine: A New Translation.