John Calvin on Isaiah 19:24

24. In that day shall Israel. Isaiah concludes the promise which he had briefly glanced at, 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 with that nation only had the Lord entered into covenant. The Lord had stretched out “his cord” over Jacob, (Deuteronomy 32:9,) as Moses speaks; {Bogus footnote} and David says,

“He hath not done so to any nation, and hath not made known to them his judgments.” (Psalm 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 includes also the rest of the nations. He does not mention them for the purpose of shewing respect, but because they were the constant enemies of God, and appeared to be more estranged from him and farther removed from the hope of favor than all others. Accordingly, though he had formerly adopted none but 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 {Bogus footnote} 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.