What does 1 Thessalonians 4:8 mean?
Paul is delivering a dire warning about the dangers of sexual impurity. The Thessalonian Christians were immersed in a culture that treated sexual sins as normal, or even as part of religious worship (1 Thessalonians 4:3–5). Such sins are not only immoral, they harm those who participate in them (1 Thessalonians 4:6–7).Paul issues an additional layer of authority in this verse. Whoever rejects these concepts of sexual immorality, and God's calling to be holy, rejects not Paul but God. After all, God had given Paul these instructions to pass along to his readers. Ignoring God's will in matters of sex is not a minor offense; it demonstrates a profound rebellion against man's Creator. God can change anyone (1 Corinthians 6:11), but those who refuse to submit to God's instructions about sexual immorality display signs of being lost (1 Corinthians 6:9–10).
Also, God had given His Holy Spirit to Paul's readers. Romans 8:9 teaches: "…Anyone who does not have the Spirit of Christ does not belong to him." Part of the Holy Spirit's ministry is to produce holy qualities in believers. Galatians 5:22–23 describes the fruit of the Spirit as "love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control." When a believer cooperates with the Holy Spirit in the process of sanctification by walking in the Spirit (Galatians 5:16) he will display the fruit of the Spirit. It should be noted that the fruit of the Spirit is a cluster of Christ-like qualities. He does not produce one quality in isolation.