From the river Euphrates; for so far David, having conquered the Syrians, extended his empire, which Solomon also maintained in that extent. And so God's promise concerning the giving of the whole land, as far as Euphrates, to the Israelites, was fulfilled. And if the Israelites had multiplied so much that the land of Canaan would not suffice them, having God's grant of all the land as far as Euphrates, they might have seized upon it whensoever occasion required. Unto the land of the Philistines, which is to be understood inclusively; for it is unreasonable to think that the Philistines were not within Solomon's dominion. Unto the border of Egypt; unto the river Sihor, which was the border between Egypt and Canaan, Joshua 13:3. Compare Genesis 15:18. Served Solomon, by tribute, or other ways, as he needed and required.
Related Commentaries of 1 Kings 4:21
1 Kings 4:21
21 And Solomon reigned over all kingdoms from the river unto the land of the Philistines, and unto the border of Egypt: they brought presents, and served Solomon all the days of his life.