Why did Israel commit sexual immorality in 1 Corinthians 10:8?
Israel committed sexual immorality because it was part of the worship of the golden calf. It was part and parcel of going back into idolatrous worship. The Corinthians faced similar temptation, living among immoral priestesses daily, and were warned to flee such things.
Les explains that Paul’s command in 1 Corinthians 10:8 not to commit fornication is tied to Israel’s example. Les asks why they committed sexual immorality and answers that it was part of the worship of the golden calf; it was part and parcel of going back into idolatrous worship. This was a real temptation to the Corinthians, who lived in the midst of it and bumped up against immoral priestesses every day. It served as a constant warning to flee from those things. Paul then continues in verse 9, warning not to test Christ, as some of them tested Him and God destroyed them with serpents.
Neither let us commit fornication, as some of them committed, and fell in one day three and twenty thousand.