Isaiah 61:4

Promises are here made to the Jews now returned out of captivity, and settled again in their own land, which are to be extended to the gospel church, and all believers, who through grace are delivered out of spiritual thraldom; for they are capable of being spiritually applied. I. It is promised that their houses shall be rebuilt (Isa 61:4), that their cities shall be raised out of the ruins in which they had long lain, and be fitted up for their use again: They shall build the old wastes; the old wastes shall be built, the waste cities shall be repaired, the former desolations, even the desolations of many generations, which it was feared would never be repaired, shall be raised up. The setting up of Christianity in the world repaired the decays of natural religion and raised up those desolations both of piety and honesty which had been for many generations the reproach of mankind. An unsanctified soul is like a city that is broken down and has no walls, like a house in ruins; but by the power of Christ's gospel and grace it is repaired, it is put in order again, and fitted to be a habitation of God through the Spirit.

— Matthew Henry's Concise Commentary (public domain)

old wastes--Jerusalem and the cities of Judah which long lay in ruins (see on Isa 58:12).

— Jamieson-Fausset-Brown Commentary (public domain)