Ezekiel 36:25

The people of God might be discouraged in their hopes of a restoration by the sense not only of their unworthiness of such a favour (which was answered, in the foregoing verses, with this, that God, in doing it, would have an eye to his own glory, not to their worthiness), but of their unfitness for such a favour, being still corrupt and sinful; and that is answered in these verses, with a promise that God would by his grace prepare and qualify them for the mercy and then bestow it on them. And this was in part fulfilled in that wonderful effect which the captivity in Babylon had upon the Jews there, that it effectually cured them of their inclination to idolatry. But it is further intended as a draught of the covenant of grace, and a specimen of those spiritual blessings with which we are blessed in heavenly things by that covenant. As (ch. 34) after a promise of their return the prophecy insensibly slid into a promise of the coming of Christ, the great Shepherd, so here it insensibly slides into a promise of the Spirit, and his gracious influences and operations, which we have as much need of for our sanctification as we have of Christ's merit for our justification. I. God here promises that he will work a good work in them, to qualify them for the good work he intended to bring about for them, Eze 36:25-27.

— Matthew Henry's Concise Commentary (public domain)

The external restoration must be preceded by an internal one. The change in their condition must not be superficial, but must be based on a radical renewal of the heart. Then the heathen, understanding from the regenerated lives of God's people how holy God is, would perceive Israel's past troubles to have been only the necessary vindications of His righteousness. Thus God's name would be "sanctified" before the heathen, and God's people be prepared for outward blessings. sprinkle . . . water--phraseology taken from the law; namely, the water mixed with the ashes of a heifer sprinkled with a hyssop on the unclean (Num 19:9-18); the thing signified being the cleansing blood of Christ sprinkled on the conscience and heart (Heb 9:13-14; Heb 10:22; compare Jer 33:8; Eph 5:26). from all your idols--Literal idolatry has ceased among the Jews ever since the captivity; so far, the prophecy has been already fulfilled; but "cleansing from all their idols," for example, covetousness, prejudices against Jesus of Nazareth, is yet future.

— Jamieson-Fausset-Brown Commentary (public domain)