The final message that an exiting pastor gives to their congregation has only one purpose; you must hand them over to God. It’s like the committal prayer at a funeral. No matter how rotten a person has been (or how rotten your pastoral tenure has been), no matter how short or long their life (or your ministry), no matter what the circumstances of their death (or the reasons for your departure), when you stand at the gravesite you hand someone over to God. People should leave your final worship service feeling like they are now in better hands. Don’t let your ego get in the way of this simple task.
I have found the benedictions of St. Paul to be particularly useful for saying good bye to a congregation. Paul was good at it. He said good bye to people all the time. His image of “one person plants, another waters, but God owns the farm” provides an apt image of the itinerant calling (I Corinthians 3:5-9). His benedictions, though, make the task of saying good bye simpler, by putting the focus on the on going power of God.
Take Romans 16:25-27:
Now to him who is able to establish you in accordance with my gospel, the message I proclaim about Jesus Christ, in keeping with the revelation of the mystery hidden for long ages past, but now revealed and made known through the prophetic writings by the command of the eternal God, so that all the Gentiles might come to the obedience that comes from faith— to the only wise God be glory forever through Jesus Christ! Amen.
A three point sermon says:
1: No matter how good of a preacher you are, it should be made clear that the Gospel doesn’t belong to you. There is one message, one baptism, one faith, one hope. It remains. Each itinerant pastor shares the same Gospel. The good news, at the heart of our faith, does not depend on who it is who is preaching it.
2: God’s plan is to establish his church. God still has a plan for the church you are leaving. The best is yet to come (say it like you mean it).
3: God is the only one that is wise (so stop trying to figure out who’s to blame for the pastor leaving). Focus on the wisdom of God and the fact that He knows best. Human understanding is way overrated.