By this therefore shall the iniquity of Jacob be purged; and this is all the fruit to take away his sin; when he maketh all the stones of the altar as chalkstones that are beaten in sunder, the groves and images shall not stand up.
By this - By the exile of Israel (the 'sending away,' Isaiah 27:8); or by the Lord's judicial debating with Israel, in the English version.
Shall the iniquity of Jacob be purged - expiated (Horsley).
And this (is) all the fruit - this is the whole benefit designed to be brought about by the chastisement-namely, the removal of his (Israel's) sin (namely, idolatry, Deuteronomy 9:21; Hosea 10:8).
When he - Yahweh.
Maketh all the stones of the altar as chalk-stones - at the destruction of Jerusalem by Nebuchadnezzar, His instrument. The Jews ever since have abhorred idolatry (cf. Isaiah 17:8).
The groves and images shall not stand up - shall rise no more (Horsley).