Isaiah 27:9

The condition of restoration and forgiveness. Thereforepoints back to the idea of Isaiah 27:7 the moderation of Israel's punishment, while By this, i.e. ("on this condition") points forward to the end of the verse, the removal of idolatrous emblems.

be purged be expiated (R.V. marg.).

and thisis all … sin Better: and this is the whole fruit of the taking away of his sin. "Fruit" seems here to mean contemplated or expected issue, "the aim."

when he maketh all the stones of the altar Rather, that he should make all altar-stones, &c.

the groves and images, &c. or, the Asherim and sun-pillars (see on Isaiah 17:8) shall not remain standing.