John Gill Commentary Deuteronomy 6:10

"And it shall be, when Jehovah thy God shall bring thee into the land which he sware unto thy fathers, to Abraham, to Isaac, and to Jacob, to give thee, great and goodly cities, which thou buildest not," — Deuteronomy 6:10 (ASV)

And it shall be, when the Lord your God shall have brought you
into the land
The land of Canaan, on the borders of which they now were, and were just going into:

which he swore unto your fathers, to Abraham, to Isaac, and to Jacob, to
give you ;
of his own free favour and good will, without any merit and desert of theirs, and in which would be found

great and goodly cities, which you built not ;
large and capacious, delightfully situated, well built, and strongly fortified, without any pains or expense
of theirs; all ready for them to take possession of, and dwell in; and so should no longer reside in tents or
booths, as they had for forty years past, but in spacious and noble cities.