1Cor 10:8

“Remember the four and twenty thousand that were rejected for fornication.”

“And of course it is a sufficient one, that so vast a number-(the number) of 24, 000-of the People, when they committed fornication with the daughters of Madian, fell in one plague. But, with an eye to the glory of Christ, I prefer to derive (my) discipline from Christ.”

“"Neither let us commit fornication, as some of them committed." Wherefore doth he here make mention of fornication again, having so largely discoursed concerning it before? It is ever Paul's custom when he brings a charge of many sins, both to set them forth in order and separately to proceed with his proposed topics, and again in his discourses concerning other things to make mention also of the former: which thing God also used to do in the Old Testament, in reference to each several transgression, reminding the Jews of the calf and bringing that sin before them. This then Paul also does here, at the same time both reminding them of that sin, and teaching that the parent of this evil also was luxury and gluttony. Wherefore also he adds, "Neither let us commit fornication, as some of them committed, and fell in one day three and twenty thousand." And wherefore names he not likewise the punishment for their idolatry? Either because it was clear and more notorious, or because the plague was not so great at that time, as in the matter of Balaam, when they joined themselves to Baalpeor, the Midianitish women appearing in the camp and alluring them to wantonness according to the counsel of Balaam. For that this evil counsel was Balaam's Moses sheweth after this, in the following statement at the end of the Book of Numbers. "Balaam also the son of Beor they slew in the war of Midian with the sword and they brought the spoils. ... And Moses was wroth, and said, Wherefore have ye saved all the women alive? For these were to the children of Israel for a stumbling-block, according to the word of Balaam, to cause them to depart from and despise the word of the Lord for Peor's sake."”

“Note that it was not just idolatry which led to death [but their immorality as well].”

“Again he mentioned fornication, so that through constant reproof he might make his word more effective. This sin also is born from gluttony. And when did twenty-three thousand perish? When, by the counsel of Balaam, the Midianite women appeared at the camp, enticed the young men to themselves, and through fornication led them to offer sacrifice to Baal-Peor, and the people who were in the camp perished (Num. 25:1–9).”