Paul opens with an appeal: as they have learned how to walk and to please God, they should do so more and more. He states plainly, For this is the will of God: your sanctification. God wants believers to be holy and pure in body and life, for God called us not for uncleanness, but in sanctification. Anyone who rejects this rejects God, who gave them the Holy Spirit.
About brotherly love, Paul says they are taught by God to love one another, and they already love all the believers in Macedonia. He urges them to abound more and more. They should make it their goal to lead a quiet life, take care of their own work, and work with their own hands. This will earn the respect of outsiders and keep them from needing help.
Then Paul gives comfort about believers who have died. He does not want them to grieve like the rest, who have no hope. He writes: For if we believe that Jesus died and rose again, even so God will bring with him those who have fallen asleep in Jesus. The Lord himself will descend from heaven with a shout, with the voice of the archangel and with God's trumpet. The dead in Christ will rise first. Then believers who are alive will be caught up together with them to meet the Lord. So we will be with the Lord forever. Paul concludes: Therefore comfort one another with these words.