The aim of your sermon is to help believers understand why Paul rebuked Peter as well as the place of old covenant laws in the new covenant church. Having done so, you will also need to explain why Paul refers to this incident in defence of his ministry. Finally, your sermon provides a chance to make several applications, with a focus on the place of God’s law and the catholicity of his church.
11 But when Cephas came to Antioch, I opposed him to his face, because he stood condemned.