Peter Pett's Commentary on the Bible
Numbers 25:16-18
‘And Yahweh spoke to Moses, saying,'
Then Yahweh added a further sentence to His judgment.
‘Vex the Midianites, and smite them, for they vex you with their wiles, with which 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.'
What had happened had been a result of a deliberate policy by the Midianites. They had hoped that by wooing Israel from Yahweh they would turn Him against them. Thus they had approved of their young women and the young women of Moab leading Israelite males astray for this purpose. It was seen to be Midianite policy (Numbers 31:16) that had brought the plague on Israel and had led so many into idolatry and death. They were thus murderers. Therefore, like the Canaanites, they had to be slain. There had to be death for death.
It is noteworthy that this section of Numbers, which has contained so much of victory should end with Israel's failure. It was Yahweh's constant reminder that pride comes before a fall. It was an early warning of how careful they must be when they entered the land.