Albert Barnes Commentary Isaiah 5:21

"Woe unto them that are wise in their own eyes, and prudent in their own sight!" — Isaiah 5:21 (ASV)

Woe to them who are wise ... – This is the fifth crime specified. It refers to those who are inflated with a false opinion of their own knowledge, and are therefore self-confident and vain. This is expressly forbidden (Proverbs 3:7): Be not wise in thine own eyes; compare (Proverbs 26:12).

In their own eyes – In their own opinion or estimation.

And prudent – Knowing; self-conceited.

This was, doubtless, one characteristic of the times of Isaiah. It is known to have been strikingly the characteristic of the Jews—particularly the Pharisees—in the time of our Savior. The evil of this was:

1. That it demonstrated and fostered pride.
2. That it rendered them unwilling to be instructed, and especially by the prophets.

As they supposed that they were already wise enough, they refused to listen to others. This is always the effect of such self-confidence; and therefore, the Savior required His disciples to be meek, humble, and teachable as children.