Numbers 25:18

For they vex you with their wiles
Not with wars, but with wiles, with cunning stratagems, and artful methods to draw them into sin, that thereby they might be exposed to the wrath of God:

wherewith they have beguiled you in the matter of Peor;
the idol Peor, that is, Baalpeor; which seems to countenance the notion that Peor was the name of a man, some great personage, who was deified after his death; now the Midianites beguiled the Israelites, by sending their daughters among them, with whom they committed fornication, and by whom they were inveigled to worship the idol Peor:

and in the matter of Cozbi, the daughter of a prince of Midian,
their sister; their countrywoman, as it was common with eastern people to call those of the same country with them their brethren and sisters: now the Midianites beguiled the Israelites, by prostituting a person of such quality to a prince of theirs, which was setting an example to other daughters of Midian to follow her, and so hereby many of the children of Israel were ensnared into whoredom, and into idolatry:

which was slain in the day of the plague, for Peor's sake:
or for the business of Peor, as the Targum of Jonathan, because of the worship of that idol; not that Cozbi was slain upon that account, but the plague came upon Israel by reason of their worshipping of it, and it was on the day that the plague was that she was slain; by which it seems that the plague lasted but one day.