Matthew Henry Commentary Numbers 25:16-18

"And Jehovah spake unto Moses, saying, Vex the Midianites, and smite them; for they vex you with their wiles, wherewith they have beguiled you in the matter of Peor, and in the matter of Cozbi, the daughter of the prince of Midian, their sister, who was slain on the day of the plague in the matter of Peor." — Numbers 25:16-18 (ASV)

We do not read that any Midianites died of the plague; God punished them with the sword of an enemy, not with the rod of a father. We must set ourselves against whatever is an occasion of sin to us (Matthew 5:29–30). Whatever draws us to sin should be a vexation to us, as a thorn in the flesh. And none will be more surely and severely punished than those who, after Satan's example, and with his subtlety, tempt others to sin.