isaiah 6:13 But yet in it shall be a tenth, and it shall return, and shall be eaten: as a teil tree, and as an oak, whose substance is in them, when they cast their leaves: so the holy seed shall be the substance thereof. - Free Bible Online

      13. and it shall return, and . . . be eaten--Rather, "but it shall be again given over to be consumed": if even a tenth survive the first destruction, it shall be destroyed by a second (Isa 5:25; Eze 5:1-5, 12), [MAURER and HORSLEY]. In English Version, "return" refers to the poor remnant left in the land at the Babylonish captivity (2Ki 24:14; 25:12), which afterwards fled to Egypt in fear (2Ki 25:26), and subsequently returned thence along with others who had fled to Moab and Edom (Jer 40:11, 12), and suffered under further divine judgments.
      tell--rather, "terebinth" or "turpentine tree" (Isa 1:29).
      substance . . . when . . . cast . . . leaves--rather, "As a terebinth or oak in which, when they are cast down (not 'cast their leaves,' Job 14:7), the trunk or stock remains, so the holy seed (Ezr 9:2) shall be the stock of that land." The seeds of vitality still exist in both the land and the scattered people of Judea, waiting for the returning spring of God's favor (Ro 11:5, 23-29). According to Isaiah, not all Israel, but the elect remnant alone, is destined to salvation. God shows unchangeable severity towards sin, but covenant faithfulness in preserving a remnant, and to it Isaiah bequeaths the prophetic legacy of the second part of his book (the fortieth through sixty-sixth chapters).

JFB.