Charles Ellicott Commentary Joel 3:18

"And it shall come to pass in that day, that the mountains shall drop down sweet wine, and the hills shall flow with milk, and all the brooks of Judah shall flow with waters; and a fountain shall come forth from the house of Jehovah, and shall water the valley of Shittim." — Joel 3:18 (ASV)

The mountains shall drop down new wine. —The material prosperity depicted in these verses symbolizes the glorious reign of Jehovah when the last enemy has been destroyed, and “God is all in all.”

A fountain shall come forth. —The spiritual fertilizing power of the knowledge of the Lord is compared to the life-giving influence of a stream of water, which causes luxuriance to the trees on its banks. This imagery is exemplified by Ezekiel, who traces the course of the waters issuing from under the threshold of the house of the Lord (Ezekiel 47:0). (Revelation 22:1.)

The valley of Shittim. —Hebrew, acacias. Shittim, in the land of Moab, is symbolic of the barrenness and sterility of land where there is no water; of the dry places of the world, where there are trees lacking moisture: the heathen, to whom God is not known, shall yet become covered with the knowledge of the Lord.