Albert Barnes Commentary Isaiah 7:20

"In that day will the Lord shave with a razor that is hired in the parts beyond the River, [even] with the king of Assyria, the head and the hair of the feet; and it shall also consume the beard." — Isaiah 7:20 (ASV)

In the same day ... - The idea in this verse is the same as in the preceding one, though presented in a different form. The meaning is that God would bring this punishment upon them, but He would use the Assyrian as an instrument to do it.

Shave - The act of shaving off the hair denotes punishment or disgrace. Compare 2 Samuel 10:4: Hanun took David’s servants, and shaved off one half of their beards; see also 1 Chronicles 19:4.

With a razor - Using them as an instrument. God here claims the power of directing them and regards them as employed by Him; see Isaiah 10:5-7.

That is hired - This is an allusion to the custom of hiring soldiers or employing mercenary armies. For instance, Great Britain employed mercenary troops, or hired bodies of Hessians from the Germans, to carry on the war in America. The meaning here is that God would employ the Assyrians as His instruments to accomplish His purposes, as if they were hired and paid by the plunder and spoil of the nation.

By them beyond the river - This refers to the river Euphrates. The Euphrates is usually meant in the Scriptures when the river is mentioned without specifying the name; Psalms 72:8; Psalms 80:2. This was the river that Abraham had crossed, and this, perhaps, was for a long time the eastern boundary of their geographical knowledge; see the note at Isaiah 11:15.

The head - The hair of the head.

The hair of the feet - That is, the hair on other parts of the body, specifically on the lower parts of the body.

Shall consume the beard - This means it shall cut off the beard. This act was considered particularly disgraceful among the Jews and is still regarded as such today among all Eastern nations.

The beard is regarded as a distinguished ornament; among Muslims, it is sworn by, and no higher insult can be offered than to treat the beard with indignity; compare the note at Isaiah 50:6. The meaning here is that God would employ the Assyrian as His instrument to lay waste the land.