John Calvin Commentary Daniel 5:22

"And thou his son, O Belshazzar, hast not humbled thy heart, though thou knewest all this," — Daniel 5:22 (ASV)

Daniel here shows why he related what we have until now heard concerning King Nebuchadnezzar’s punishment: Belshazzar should have been so affected by that domestic example as to submit himself to God. We may believe, indeed, that his father Evil-Merodach had forgotten his punishments, since he would not have conducted himself so insolently against God, nor trampled on true and sincere piety (implying that if he had remembered, his conduct would have been different); for God spared the wretched tyrant who restrained himself within the bounds of moderation.

But as for Belshazzar, he was altogether intolerable; therefore God stretched forth His hand. The Prophet now teaches this. Thou art his son, he says. This circumstance more strongly emphasized Belshazzar's duty not to seek examples in foreign nations, since he had a sufficient one at home that was both necessary and useful.

He enlarges upon Belshazzar’s crime in another way, by saying, Yet thou didst know this. Men are accustomed to shield themselves with their ignorance to lessen the guilt of their crimes, but those who sin knowingly and willfully are without the slightest excuse.

The Prophet therefore convicts the king of manifest obstinacy; it is as if the Prophet had said, "You have provoked God’s anger on purpose." This is because Belshazzar should have been aware of the horrible judgment awaiting all the proud, especially when he had such a remarkable and unique proof of it in his grandfather, which he should have kept constantly before his eyes.