כִּ֤י כַבֶּ֙גֶד֙ יֹאכְלֵ֣ם עָ֔שׁ וְכַצֶּ֖מֶר יֹאכְלֵ֣ם סָ֑ס וְצִדְקָתִי֙ לְעוֹלָ֣ם תִּֽהְיֶ֔ה וִישׁוּעָתִ֖י לְד֥וֹר דּוֹרִֽים׃ (ס)
For the moth shall eat them up like a garment, And the worm shall eat them like wool; But My favour shall be for ever, And My salvation unto all generations.
Ibn Ezra on Isaiah
סס The worm. It is hap. leg. But my righteousness shall be for ever. Comp. And His righteousness endureth for ever (Ps. 112:8).8I. E. comparing this phrase with a similar one (Ps. 112:3) explains the verb היה by the verb עמד, which more exclusively expresses duration, while היה has also the meaning to become, signifying a single act.