John Calvin Commentary Numbers 25:17

"Vex the Midianites, and smite them;" — Numbers 25:17 (ASV)

Vex the Midianites, and smite them. Since God constantly forbids His people to take vengeance, it is surprising that the people of Israel should now be instigated to do so, as if they were not already more than enough disposed to it.

We must bear in mind, however, that since God, who is the just avenger of all wickedness, often employs human agents and appoints them as lawful ministers to carry out His vengeance, this type of vengeance must not be entirely condemned without exception.

Only such vengeance as people themselves are impelled to by carnal passions is to be condemned. If anyone is injured, he is immediately carried away to the desire of vengeance by the impulse of his own personal injury, and this is manifestly wrong.

But if a person is led to inflict punishment by a just and well-regulated zeal towards God, he undertakes not his own cause, but God's.

God did not, therefore, desire to give free rein to His people’s anger, allowing them to repay the Midianites as they deserved, driven by the violence of impulsive anger. Instead, He armed them with His own sword for their punishment, as if He had declared that there was a just cause for their war and that they need not fear the charge of cruelty if they exterminated such detestable enemies.

For although Balaam alone had imagined this snare, still the guilt is laid upon the whole people. In the meantime, the punishment of the Moabites is delayed, although they had apparently inflicted the greater injury.

Since no clear reason appears here why God should mercifully bear with the one nation while He quickly hastens to punish the others, let us learn to regard His judgments with reverence and not presume to discuss them further than is lawful.

Let it be sufficient for us to know that war was justly declared against the Midianites, because it was not due to any lack of effort on their part that Israel was not ruined by their wicked impiety.¹⁹⁰

¹⁹⁰ “Par l’impiete a laquelle ils l’induisoyent;” by the impiety to which they induced them. — Fr.