According to 1 Corinthians 6, we should flee from what?

Answer: Sexual immorality

Flee from sexual immorality. All other sins are outside the body, but this sin is against one's own body.

“Flee from sexual immorality. Every other sin a man can commit is outside his body, but he who sins sexually sins against his own body.”— 1 Corinthians 6:18 (BSB)