Every culture defines what and who is, and is not, acceptable. But God's family is not confined to one culture; it is international and universal (Colossians 1:6). We are welcomed as part of His family when we receive the Lord Jesus Christ as Saviour and Lord (John 1:12). How do we know about Him? Somebody told us what the apostles have written (2 Timothy 2:8). The apostles were given the right to define the gospel. There is no other true and saving gospel (Galatians 1:6-9).

In the same way, the apostles have the authority of Jesus to define what is 'sound doctrine' – that is, teaching which has God's seal of approval (Titus 1:9). What the Lord Jesus personally revealed to Paul was exactly the same as He had previously taught Peter and James (Galatians 1:15-24). God deposited His truth in the apostles, giving them the responsibility to say how God wanted His people to live and communicate.

When Paul set the boundaries of fellowship, as in this passage, he did so 'in the Name of the Lord Jesus Christ' (2 Thessalonians 3:6). The Scriptures do not allow for subsequent 'improved' interpretations: any such opinions do not have divine authority and their authors are condemned (Revelation 22:18-19). So this instruction, to disassociate from believers who refused to obey Paul's lifestyle instructions, has God's seal of authenticity. The purpose is restorative: so that those who wander from the plumb-line of apostolic teaching might feel shame and repent. The errant believer is not to be hated but loved.

Individualism has become a plague of a million opinions. But Jesus is always right: and He has entrusted His gospel and disciple-making to the apostles (Matthew 28:16-20). Therefore, like the Early Church we must be devoted to what the apostles taught (Acts 2:42). Most of the believers in the world are Gentiles, and as Paul is the Apostle to the Gentiles (Galatians 2:8) we have no right to frustrate God's will by ignoring what Paul has written. Believers who persist in decrying Paul's writings should be warned and warned again, but after that they have no right to corrupt the fellowship; they should be excluded until they repent (Titus 3:10-11).