Isaiah 48:21

And they thirsted not when he led them through the deserts,.... As when he led the people of Israel through the wilderness to Canaan's land, though they sometimes thirsted for want of water, yet they were supplied with it, by which their thirst was extinguished, to which the reference here is. So when they came out of Babylon, and passed through the waste and desert places which lay between that and Judea, they were supplied with all necessaries. Thus the apostles of Christ, when they travelled through the Gentile world, comparable to a desert, publishing redemption and salvation by Christ, had every needful supply, both of temporal and spiritual things; they lacked not any thing. In like manner the people of God, while they pass through the wilderness of this world to the heavenly glory, are furnished and refreshed with living water out of the fountain and fulness of grace in Christ, of which if a man drink, he shall thirst no more, John 4:14

Isaiah 49:10: he caused the waters to flow out of the rock for thee; that is, for the Israelites in the wilderness, when they were come out of Egypt, and wanted water, Exodus 17:6:

he clave the rock also, and the waters gushed out; Psalms 78:15, the rock was a type of Christ, from whom the living waters of grace flow, to the support, supply, comfort, and refreshment of the saints in this world, 1 Corinthians 10:4. Grace is often signified by waters, because purifying and cleansing, reviving and refreshing, softening and fructifying, and an extinguisher of thirst: their gushing out denotes the abundance of it, which is received from Christ, not only at first conversion, in the regeneration and quickening of men; in the pardon of their sins, and the justification of their persons; but in the large communications of grace, after made, for the supply of their wants: and all which come from Christ the Rock, that is higher than they, from whence their bread is given them, and their waters are sure unto them; and who is the Rock of their refuge and salvation: and the cleaving of this Rock may signify his sufferings and death; his being smitten, bruised, and broken for his people, that they may partake of his grace, and the blessings of it.