Albert Barnes Commentary Joshua 1:4

"From the wilderness, and this Lebanon, even unto the great river, the river Euphrates, all the land of the Hittites, and unto the great sea toward the going down of the sun, shall be your border." — Joshua 1:4 (ASV)

Lebanon is spoken of as “this Lebanon,” because it was visible from the neighborhood in which Israel was encamped. (Compare Deuteronomy 3:8-9.) “The wilderness” of the text is the Desert of Arabia, which forms the southern, as Lebanon does the northern limit of the promised land. The boundaries on the east and west are likewise indicated, and the intervening territory is described generally as “all the land of the Hittites.”

The Hittites are properly the inhabitants of northern Canaan and Phoenicia (see Exodus 3:8 note), but the name appears to be used here for the Canaanites in general, as in 1 Kings 10:29. On the boundaries of the promised land, compare Deuteronomy 11:24; Genesis 15:18.