John Gill Commentary Deuteronomy 4:22

"but I must die in this land, I must not go over the Jordan; but ye shall go over, and possess that good land." — Deuteronomy 4:22 (ASV)

But I must die in this land
The land of Moab, in a mountain in it he died, and in a valley there he was buried, (Deuteronomy 32:50) (Deuteronomy 34:5Deuteronomy 34:6) ,

I must not go over Jordan ;
this he repeats, as lying near his heart; he had earnestly solicited to go over, but was denied it:

but you shall go over, and possess that good land ;
this he firmly believed and assures them of, relying on the promise and faithfulness of God.