John Wesley on Joel 3:18

The mountains - The vines planted upon the mountains. Shall flow - So fruitful shall the hills be, that milk shall abound every where. A fountain - The prophet alludes to those waters which were conveyed from some spring through conduit pipes towards the altar. This no doubt is a shadow of the purifying blood of Christ, and his sanctifying spirit and word. And in that it is said to come from the house of the Lord, it intimates that this saving grace shall be first preached from Jerusalem, and by the church, which is the house of God, shall be published to others. Shittim - Was a place in the plains of Moab. These spiritual waters shall flow down to the dry and thirsty, the barren and fruitless Gentiles, and make them fruitful.