Adam Clarke, on Ezek 47:1

Behold, waters issued out from under the threshold - Ezekiel, after having made the whole compass of the court of the people, is brought back by the north gate into the courts of the priests; and, having reached the gate of the temple, he saw waters which had their spring under the threshold of that gate, that looked towards the east; and which passing to the south of the altar of burnt-offerings on the right of the temple, ran from the west to the east, that they might fall into the brook Kidron, and thence be carried into the Dead Sea. Literally, no such waters were ever in the temple; and because there were none, Solomon had what is called the brazen sea made, which held water for the use of the temple. It is true that the water which supplied this sea might have been brought by pipes to the place: but a fountain producing abundance of water was not there, and could not be there, on the top of such a hill; and consequently these waters, as well as those spoken of in Joe 3:18, and in Zac 14:8, are to be understood spiritually or typically; and indeed the whole complexion of the place here shows, that they are thus to be understood. Taken in this view, I shall proceed to apply the whole of this vision to the effusion of light and salvation by the outpouring of the Spirit of God under the Gospel dispensation, by which the knowledge of the true God was multiplied in the earth; and have only one previous remark to make, that the farther the waters flowed from the temple, the deeper they grew. With respect to the phraseology of this chapter, it may be said that St. John had it particularly in view while he wrote his celebrated description of the paradise of God, Revelation 22. The prophet may therefore be referring to the same thing which the apostle describes, viz., the grace of the Gospel, and its effects in the world.