John Calvin Commentary Isaiah 5:21

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

Wo to them that are wise in their own eyes! Here he proceeds to rebuke those on whom no instruction can produce a good effect, and who do not allow any wise counsels or godly warnings to be received. In short, he pronounces a curse on obstinate scorners, who set up either the lusts of the flesh or a preposterous confidence in their wisdom, in opposition to God’s instruction and warnings. And not only does he rebuke those who are puffed up with a false conviction of their wisdom, and are ashamed to learn from others, but he likewise pronounces a general condemnation on all who, through prejudices in their own favor, refuse to hear God speaking, and to listen to his holy warnings.

This fault has been too common in all ages, and we see it in many people today, who, though they would shrink from openly rejecting the doctrine of godliness, are yet so far from being truly obedient and teachable, that they haughtily reject everything that does not please them. They acknowledge that they need some bridle, but, on the other hand, are so much blinded by their presumption, that, when God points out the way, they immediately rebel; and not only that, but they also break out into violent indignation at the censure of their conduct. Indeed, where is the person who renounces their own judgment and is ready to learn only from the mouth of God? But nothing is more destructive than this deceitful show of wisdom, for the beginning of piety is willingness to be taught, when we have renounced our own judgment and follow wherever God calls.

Nor is this false belief condemned solely because it makes people disobedient to God and thus causes their ruin, but also because it is, in itself, something God cannot endure. We must become fools if we desire to be God’s disciples. But it is also certain that mad rebellion reigns wherever that modesty and humility is not found which leads a person willingly to yield subjection. In their own eyes means what we say in French, a leur semblant, that is, in their own conceit.