Numbers 26:18

for they vex you, prove themselves your most dangerous enemies, with their wiles, wherewith they have beguiled you in the matter of Peor, by seducing them to idolatrous practices, and in the matter of Cozbi, the daughter of a prince of Midian, their sister, which was slain in the day of the plague for Peor's sake. Thus the zeal of Phinehas, the zeal for Jehovah, might be assumed by all the nation and the honor of the Lord be vindicated. It had been an extreme case of the grossest outrage that this princess had caused herself to be led into the sacred camp, to glorify lust, and to render it an act of service or worship. This command of God was carried out Numbers 31:1.

These are the families of the children of Gad according to those that were numbered of them, forty thousand and five hundred (40,500).