How is today's Gospel a mission text? Why not use Matthew 28 instead? Before the Church's apostles go anywhere, they must be trained. First, they must be taught the content to be preached. Second, they must be conformed to Christ's image. Christ does indeed teach, in the text, the central message to be preached. But right after, two disciples get greedy. Jesus is about to die - how could they be so self-serving?
The Son was sent by the highest Authority. He was thus authorized to send the apostles. But they were selfish. Later they would remember this day, when Jesus spoke with them about the true meaning of authority: the one who wishes to lead must become the slave of all. The Cross is the center of the Church, its message, and its reason for being. Pastors are called simply to serve all, to obey Jesus Christ.
How? They forgive sins - how audacious is that! - because they've been told by Christ to do so. They baptize - or rather, Jesus Himself baptizes. They serve us the Lord's Supper - Jesus giving it by Himself. As sinners, we want to be next to Him during His triumphal cup of suffering. But we can't drink this cup; only He can (and did) forgive the world's sins. Now we drink the cup of God's blessing, not of God's wrath. Having been crucified with Christ, we live with Him in us. By these means He conforms pastors to Himself.
This sermon is from an off-campus church, which had a guest preacher.