1 Corinthians 10:8

Second, the Israelites practiced immorality (lit. fornication) when they participated in one of the Moabites’ religious feasts (Numbers 25:1-9). Paul said 23,000 Israelites died in one day. Moses in Numbers 25:9 said 24,000 died as a result of the plague God sent to judge the people. There is, therefore, no conflict between the numbers since they describe somewhat different groups of people. Another explanation that has been suggested is that the larger number included Israel’s leaders, and the smaller one did not. If immorality is only implicit in the record of the Golden Calf incident, it is explicit in the account of the Baal Peor incident. Clearly this was taking place in the Corinthian church (1 Corinthians 5:1-5; 1 Corinthians 5:10-11; 1 Corinthians 6:9-10; 1 Corinthians 6:12-20). Some modern Christians have participated in fornication that unbelievers have lured them into.