(Isa. 10:22)
The Old Testament formula for an apostate people’s return to God is found in 2 Chronicles 30:6–9. These verses speak of Israel’s return to the promised land, to God through repentance, and to true temple worship. The expression “as the sands of the sea” recalls the Abrahamic covenant that speaks of Abraham’s posterity becoming as numerous as the sands of the sea (Gen. 22:17; Abr. 3:14). Although the number of children of Israel will be exceedingly high, only a remnant will return… . The great stretch of sandy seashore next to the Mediterranean Sea together with the immense deserts of sand throughout the Near East have made sand the subject of many similes in the scriptures.
(Donald W. Parry, Visualizing Isaiah [Provo, Utah: The Foundation for Ancient Research and Mormon Studies, 2001], 101.)
Isaiah declared that the people of Israel will have become so numerous that Jacob’s descendants will be as the countless sands of the sea. He also hints that out of these many millions of heirs to the latter-day kingdom, only a “remnant” will elect to return. After that, God’s great “consumption” or cleansing will take place so that the earth can overflow with righteousness.
(W. Cleon Skousen, Isaiah Speaks to Modern Times [Salt Lake City: Ensign Publishing Co., 1984], 236.)