The connector For introduces the reason why the Israelite exiles should not be afraid or upset by the verbal attacks from others. The reason is that their opponents will not last long. This contrasts with the repeated assurance that God will rescue his people permanently.

The moth will eat them up like a garment describes the fate of those who criticize the righteous. It uses the same simile as in 50.9 (see the comments there). In all similes it is important to identify the nature and the extent of the comparison being made. In the same way as a moth spoils clothing so that it becomes useless, so the opponents of God’s people will become powerless and unable to harm them anymore. This simile does not refer to the complete destruction of Israel’s enemies, but to their inability to do any more harm.

And the worm will eat them like wool is parallel to the previous simile. A worm that eats holes in fabric makes it useless. In the same way those who insult the faithful among the exiles will become powerless to do harm. A worm is the larva of a moth. The larvae, not adult moths, are actually responsible for spoiling clothes. For wool see 1.18.

Good News Translation and Bible en français courant combine the first two lines of this verse. Good News Translation has “they will vanish like moth-eaten clothing!” and Bible en français courant says “because they will suffer the fate of woolen clothing that is devoured by moths.” However, both these renderings suggest complete destruction rather than making something unusable.

But my deliverance will be for ever, and my salvation to all generations: The contrastive conjunction But introduces these two parallel lines. The exiles’ opponents will not last forever, but God assures his people of permanent rescue. He will rescue them from Babylonia, so that they can return to Jerusalem. The promise God makes here is almost identical to the one in verse 6 (see the comments there). He repeats it to emphasize the certainty of what he will do for his people. The Hebrew expressions rendered for ever and to all generations refer to the longest time one can imagine rather than eternity in the modern sense.

Translation examples for this verse are:

• Because moths will eat them up as though they were clothing,
and worms will devour them as though they were wool.
But I will rescue them for an eternity,
I will save them forever.”

• For a moth will eat holes in them as in a garment,
and its worms will devour them as in wool.
Yet my deliverance of them will be permanent,
my rescuing them will be forever.”

Quoted with permission from Ogden, Graham S. and Sterk, Jan. A Handbook on Isaiah. (UBS Helps for Translators). New York: UBS, 2011. For this and other handbooks for translators see here .