Sometimes prophecy is quite general in nature. Other times it is very detailed. The Promised Land prophecies fall into both categories. God promised Abraham “Unto your seed will I give this land” (Genesis 12:7). “This land” is rather general.
But God later repeated the promise with great detail: “Unto your seed have I given this land, from the river of Egypt unto the great river, the river Euphrates: the Kenites, and the Kenizzites, and the Kadmonites, and the Hittites, and the Perizzites, and the Rephaims, and the Amorites, and the Canaanites, and the Girgashites, and the Jebusites” (Genesis 15:18-21). What is “the river of Egypt”? The Nile must be ruled out for one simple reason. The Egyptians are not listed as one of the nations to be conquered. Zondervan Pictorial Bible Dictionary defines “river of Egypt,” as “a brook (RSV) on the SW border of Palestine flowing into the Mediterranean Sea (Gen.15:18; Num.34:5). Now Wadi el Arish.”
Was this promise–prophecy ever fulfilled? Some say “no,” and relegate its fulfillment to a future “millennium.” But 2 Chronicles 9:26 says of Solomon: “And he reigned over all the kings from the river even unto the land of the Philistines, and to the border of Egypt.” The NAS here renders “the river” as “the Euphrates River.” The NKJ, in a footnote, says “The Euphrates.” “The River” in this text is understood to be the Euphrates, just like it is in Isaiah 7:20.
God promised Israel land from the border of Egypt to the River Euphrates. God kept His Word, just like He always does. We can count on our God.