What does Matthew 20:28 mean?

Jesus has told His ambitious disciples a shocking thing. If they would be great, they must become a servant to the others. If they would be first, they must become slaves to each other (Matthew 20:25–27). Is Jesus just spiritualizing the idea of greatness to mean something religious? Who would willingly lead the life of a servant or slave if he really wanted greatness?

Christ points out that this is exactly the life He has been living among them. Using the title He often applied to Himself, He says the Son of Man did not come to be served, but to serve others. In fact, He came to voluntarily give His own life away as a ransom for many (1 Timothy 2:5–6). Jesus' death on the cross, which will happen quite soon, is the ultimate act of service by the greatest human ever to live (Mark 8:31). In Philippians 2:5–8, Paul explains it this way:

"Have this mind among yourselves, which is yours in Christ Jesus, who, though he was in the form of God, did not count equality with God a thing to be grasped, but emptied himself, by taking the form of a servant, being born in the likeness of men. And being found in human form, he humbled himself by becoming obedient to the point of death, even death on a cross."

This unimaginable act of service to humanity led, in the end, to Jesus becoming the greatest of all for all time:

"Therefore God has highly exalted him and bestowed on him the name that is above every name, so that at the name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father" (Philippians 2:9–11).

Jesus is calling the disciples (and all who are in Christ) to follow the same path to greatness: humble, sacrificial service to each other.