For in that day - That is, in the invasion of Sennacherib, and the events that shalt be consequent thereon.
Every man shall cast away his idols - (see the note at Isaiah 30:22; compare the note at Isaiah 2:20).
For a sin - Or rather, the sin which your own hands have made. The sense is, that the making of those idols had been a sin, or sin itself. It had been “the” sin, by way of eminence, which was chargeable upon them.