Believing in Jesus is the start of a whole new set of relationships. Each person who repents and receives Jesus as their Lord and Saviour is made a child of God (John 1:12). Because they all have the same heavenly Father, they are all brothers and sisters (Ephesians 4:6). That applies not just in the local church but world-wide. All God's children are all equal in His sight, which is why Paul urged the Thessalonian believers to express that equality as they related together.
 
As in a loving human family, Christians should treat each other with respect because of the love God has put into their hearts for each other. But having recently come into the family of God, many people in Thessalonica had brought their pride and prejudices with them. Men and women, slaves and their masters, Jews and Gentiles had to learn a new way of living in which class, race, gender and religious background would no longer get in the way of genuine love (Galatians 3:28).
 
However, some needed rebuke because their lifestyle was not godly, while others needed extra encouragement. Patience was needed along with active care of people who could not help themselves. Angry and vengeful people had to be taught to forgive; and proud people needed to serve others. Paul insisted that relating with spiritual siblings in a godly way was as important as believing the right doctrines about salvation (Luke 8:21).
 
All believers are responsible before God to learn how to relate with other children of God in a way which pleases Him. There is no place for arguments or laziness, despising the weak or failing to forgive. But such behaviour is sometimes as common in the church as in some homes. It is wrong and must stop. It does not glorify God, commend the gospel or enable the church to be light in a dark world. But many people have never thought it matters. That is why Paul's words are a necessary rebuke, warning and encouragement for us. It never hurts to put this into practice. Find some people who are difficult, different or whom you dislike: love them, forgive them and serve them (John 13:34-35). Then see how your new attitude and their response will enable the local church, and your workplace Christian fellowship, to grow.