What is the ultimate purpose of the destruction of the flesh in 1 Corinthians 5?
The ultimate purpose is not spiritual annihilation but the saving of the spirit in the day of the Lord Jesus. The flesh is delivered to Satan for physical destruction so open sin stops bringing reproach to Christ's name, while the believer's soul and spirit remain secure.
Les explains that Paul is not demanding the destruction of this man's soul and spirit, because the man is a believer. The flesh, soul, and spirit are not the same. The church, gathered with Paul's spirit and the power of the Lord Jesus, could deliver such a one to Satan to destroy his physical life or flesh. Satan can go only as far as God permits, as with Job. If this couple would not clean up their act and come away from open sin, they should be turned over to Satan to destroy the flesh and take their lives physically, lest they keep bringing reproach to the name of Christ. Yet this does not mean spiritual annihilation; the purpose is that the spirit may be saved in the day of the Lord Jesus. Les notes this is hard for many to comprehend, that people living in such sinful condition are still saved, but they will not get away with it.