John Calvin Commentary Isaiah 19:24

"In that day shall Israel be the third with Egypt and with Assyria, a blessing in the midst of the earth;" — Isaiah 19:24 (ASV)

In that day Israel shall. Isaiah concludes the promise at which he had briefly glanced, that the Egyptians and Assyrians, as well as Israel, shall be blessed. Formerly, the grace of God was in some measure confined to Israel, because only with that nation had the Lord entered into covenant. The Lord had stretched out his cord over Jacob (Deuteronomy 32:9), as Moses speaks; and David says,

He has not done so to any nation, and has not made known to them his judgments. (Psalms 147:20).

In a word, the blessing of God dwelt solely in Judea, but he says that it will be shared with the Egyptians and Assyrians, under whose name he also includes the rest of the nations. He does not mention them for the purpose of showing respect, but because they were the constant enemies of God, and appeared to be more estranged from him and further removed from the hope of favor than all others. Accordingly, though he had formerly adopted only the children of Abraham, he now wished to be called, without distinction, “The father of all nations.” (Genesis 17:7; Exodus 19:5–6; Deuteronomy 7:6, 14:2).

Israel shall be the third blessing. Some render it, Israel shall be the third. I do not approve of that rendering; for the adjective being in the feminine gender, ought to be construed with the noun ברכה, (berachah), blessing, and blessing means here a form or pattern of blessing.