Numbers 25:9
9 And those that died in the plague were twenty and four thousand.
1 Corinthians 10:8
8 Neither let us commit fornication, as some of them committed, and fell in one day three and twenty thousand.
This is a well-known alleged contradiction. Did 23,000 or 24,000 people die due to fornication?
Firstly, we can recognize that if 24,000 died, it is also true that 23,000 died, and one account is just being less precise.
However, Paul is careful to specify that 23,000 fell in one day. That leaves 1,000 that died later.
Paul was a pharisee before he converted, meaning he was well-versed in Jewish tradition. It is likely that he is drawing from that tradition here.