To effect the cleansing of the Church, the apostle commanded that the abominable ‘brother’ be expelled from the Church (vs. 2-5,7,13). This was in the interest of the sinner – ‘brother’.
Through the excommunication, he would have emotional pain from lack of association of the brethren, leading him to genuine repentance, restoration and the eventual saving of his soul (1Cor. 5:5).
The nature and magnitude of chastisement depend on the nature and magnitude of the offence committed. (1Cor. 5:2-5,9-13)
Chastisement can take the form of a private or public rebuke (Ex. 32:19-21; I Sam. 15:13, 2Chron. 16:9; 1Tim. 5:20), relieving the offender of assignments committed to him/her in the church, giving the offender a back seat, or even excommunication from the church as in the case, depending on the nature and magnitude of the chastisement, it must be born out of love and for the good of the chastised, else it is devilish (cons. 1Cor. 5:5; Heb. 12:6-10).
Furthermore, the magnitude and duration of chastisement must not be allowed to cause backsliding of the penitent offender (cons. 2Cor. 2:3-8).
Again, in his bid to ensure that the Corinthian Church was kept pure, the apostle commanded them not to keep company with any person who claimed to be a brother/sister, but lived in sin (1Cor. 5:11). This rule must still be kept today if any congregation must be kept pure (cons. 1Cor. 15:33).