John Calvin Commentary Numbers 12:11

"And Aaron said unto Moses, Oh, my lord, lay not, I pray thee, sin upon us, for that we have done foolishly, and for that we have sinned." — Numbers 12:11 (ASV)

And Aaron said to Moses, Alas! my lord. Although Aaron was aware that, through God’s indulgence, his own punishment was remitted, he still did not cease to consider what he had deserved. For we ought not to wait until God strikes us; instead, since in chastising others He invites us to repentance, even if He may spare us, we should profit promptly from their punishments. Therefore, his sister's disfigurement alarmed and terrified Aaron, so that, examining his own condition, he acknowledged himself to be deserving of a similar judgment.

His humble prayer shows that those high aspirations which had carried him away into unholy jealousy were subdued. Moses, who was younger than himself and whose superiority he had just before been unable to endure, he now calls his lord, and confesses himself to be subject to his authority and power. Thus, the dread of punishment was the best medicine to cure his disease of ambition.

In imploring Moses not to impute his sin to him, he does not usurp for mortal man a right which God, through Isaiah, claims for Himself alone;⁴⁶ rather, because Moses had been injured, he asks his pardon, lest Moses' accusation bring him before the divine tribunal.

When he confesses his own and his sister’s foolishness, he does not lessen the severity of his crime, as most people do when they generally seek to cover their transgressions with the plea of error or thoughtlessness. Instead, it is precisely as if he had said that they were senseless and out of their minds, as we gather from the next clause, in which he plainly acknowledges their guilt.

The comparison he introduces makes it evident that Miriam's leprosy was of no ordinary kind, for nothing can be more disgusting than the dead body of an undeveloped fetus, corrupt with pus and decay.

⁴⁶ No reference is here given by C. He probably alludes to He probably alludes to Isaiah 43:25..