John Chrysostom — as excerpted in the Catena Aurea on John 7:37-39

“(Hom. li. 1) He says, rivers, not river, to shew the copious and overflowing power of grace: and living water, i. e. always moving; for when the grace of the Spirit has entered into and settled in the mind, it flows freer than any fountain, and neither fails, nor empties, nor stagnates. The wisdom of Stephen, the tongue of Peter, the strength of Paul, are evidences of this. Nothing hindered them; but, like impetuous torrents, they went on, carrying every thing along with them.”