Charles Ellicott Commentary Isaiah 51:13

"and hast forgotten Jehovah thy Maker, that stretched forth the heavens, and laid the foundations of the earth; and fearest continually all the day because of the fury of the oppressor, when he maketh ready to destroy? and where is the fury of the oppressor?" — Isaiah 51:13 (ASV)

As if he were ready. —Better, as he makes him ready to destroy.

The Authorized Version unduly minimizes the amount of danger.

In the case contemplated by the prophet, the oppressor was the Babylonian monarchy, which he sees as already belonging to the past; but the words have, of course, a far wider application.