John Gill Commentary Deuteronomy 4:38

"to drive out nations from before thee greater and mightier than thou, to bring thee in, to give thee their land for an inheritance, as at this day." — Deuteronomy 4:38 (ASV)

To drive out nations from before you, greater and mightier
than you are
The seven nations of the land of Canaan, which were more in number and mightier in power and strength than they, and particularly the Amorites, who were already driven out and dispossessed of their country, even the kingdoms and nations of Sihon and Og:

to bring you in to give you their land for an inheritance, as [it is]
this day ;
referring, as Aben Ezra observes, to the inheritance of the land of the two kings of the Amorites, which the tribes of Reuben and Gad, and the half tribe of Manasseh, were put into the possession of already.