Isaiah 10:22
20 At that time those left in Israel, those who remain of the family of Jacob, will no longer rely on a foreign leader that abuses them. Instead they will truly rely on the Lord, the Holy One of Israel. 21 A remnant will come back, a remnant of Jacob, to the mighty God. 22 For though your people, Israel, are as numerous as the sand on the seashore, only a remnant will come back. Destruction has been decreed; just punishment is about to engulf you. 23 The Sovereign Lord of Heaven’s Armies is certainly ready to carry out the decreed destruction throughout the land. 24 So here is what the Sovereign Lord of Heaven’s Armies says: “My people who live in Zion, do not be afraid of Assyria, even though they beat you with a club and lift their cudgel against you as Egypt did. 25 For very soon my fury will subside, and my anger will be directed toward their destruction.” 26 The Lord of Heaven’s Armies is about to beat them with a whip, similar to the way he struck down Midian at the rock of Oreb. He will use his staff against the sea, lifting it up as he did in Egypt.
Romans 9:28
27 And Isaiah cries out on behalf of Israel, “Though the number of the children of Israel are as the sand of the sea, only the remnant will be saved, 28 for the Lord will execute his sentence on the earth completely and quickly.” 29 Just as Isaiah predicted, “If the Lord of Heaven’s Armies had not left us descendants, we would have become like Sodom, and we would have resembled Gomorrah.” 30 What shall we say then?—that the Gentiles who did not pursue righteousness obtained it, that is, a righteousness that is by faith, 31 but Israel even though pursuing a law of righteousness did not attain it. 32 Why not? Because they pursued it not by faith but (as if it were possible) by works. They stumbled over the stumbling stone, 33 just as it is written, “Look, I am laying in Zion a stone that will cause people to stumble and a rock that will make them fall, yet the one who believes in him will not be put to shame.”
Notes and References
"... It is worth noting that Paul mentions Isaiah twice by name in the short span of only three verses (9:27-29), indicating the significance of this particular book of prophecy to his understanding of the present circumstances of Israel. Some scholars believe that Romans 9:27-29 appear to be a conflation of Isaiah 10:22-23 and Isaiah 1:9. A comparison of the texts concerned shows that Paul’s citation remains at points close to and yet distinct from the MT and the Greek text of Isaiah 10:22-23 ... Isaiah 10:22-23 in its original context speaks of the salvation of the remnant of Israel when Yahweh has executed his judgment on the whole earth (Isaiah 10:23). Two things about the text are in order. First, it should be noted that in the Greek text of Isaiah and Paul’s text, the word ‘only’, which appears in most English translations, does not actually exist. Admittedly, a contrast between the original number of nation Israel and the limited number of survivors might be implied, but the point of emphasis of Isaiah does not seem to be on the contrast between the number of Israelites and the remnant, but rather on the notion that ‘the survivors will be saved’. The existence of the survivors/remnant, and indeed Israel as a nation, from start to finish is based on God’s faithfulness. God is faithful to Israel both in the history of her initial conception and in the midst of her judgment ..."
Kwok, Hon Lee The Use of Isaiah in the Pauline Letters with Special Reference to His Self-Conception of being an Apostle to the Gentiles (pp. 123-125) The University of Edinburgh, 2009