Glossa Ordinaria

And he showed. After he had shown the site of the city, its dignity, and the walls and the foundations, he describes the refreshment which God has furnished to the city, both in the present and, most of all, in the time to come. In the presence of the Godhead, or in the imitation of the life of the Lamb, who set forth in himself an example for us. A river. That is, flowing water, that is, eternal beatitude. In the appearance of water is denoted the washing of baptism, by which one comes to that beatitude. From the throne of God. That is, from those in whom God shall principally sit, because he is in them most of all, and through their instruction the lesser ones shall be crowned.