The aim of your sermon is to help believers understand the nature of the meeting that took place between Paul and the apostles in Jerusalem and why the outcome was so significant for the wider church. Having done so, you will also need to explain why Paul refers to this outcome/meeting in defence of his ministry. Why would the Galatians be encouraged to hear of the unity between Paul and the other apostles? Finally, your sermon should emphasize that good works, although they are necessary for the Christian, they are not necessary for salvation.