To deliver such an one unto Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.
Besides excommunication (which the Corinthians had the power of), Paul delegates here to them his power as an inspired apostle, of inflicting corporeal disease or death in punishment for sin ("to deliver х paradounai (G3860), temporarily; not ekdounai (G3860), to give up utterly] unto Satan such an one" - i:e., so heinous a sinner). See instances, Acts 5:1-11; Acts 13:11; 1 Timothy 1:20. As Satan receives power to try the godly, as Job (Job 2:4-7), Paul (2 Corinthians 12:7), and Peter (Luke 22:31), much more the ungodly. Satan, the "accuser of the brethren" (Revelation 12:10), the "adversary" (1 Peter 5:8), demands the sinner's punishment for sin (Zechariah 3:1; Luke 13:16). God lets Satan have his way at times (cf. Psalms 109:6). Here it is not finally, but for the affliction of the body (1 Corinthians 11:30; 1 Corinthians 11:32), so as to destroy fleshly lust (Matthew 5:29). He does not say, 'for the destruction of the body,' for it shall share in redemption (Romans 8:23); but of the corrupt "flesh," which "cannot inherit the kingdom of God," and the lusts of which prompted this offender to incest (Romans 7:5; Romans 8:9-10; Romans 8:13). The "destruction of the flesh" answers to "mortify the deeds of the body," only that this is done by one's self, that by chastisement from God (cf. 1 Peter 4:2; 1 Peter 4:6).
The spirit may be saved - the spiritual part, in believer the organ of the Holy Spirit, involving the salvation of the body too. Temporary affliction often leads to permanent salvation (Psalms 83:16). Satan in God's hand becomes, in spite of himself, an instructor of believers.