What does Mark 10:31 mean?

Jesus tries to drive this idea into the disciples' minds several times, in several different ways (Mark 8:34–35; 9:35; 10:42–45), but this may be the only occasion where the disciples are compared favorably. The rich young man would have been seen as first in the earthly world, with his wealth, and first in the ancient religious world with his history of following the law. Yet he is last in the kingdom of God. This is partially because he refuses to surrender his worldly blessings for the kingdom. It's also because he refuses to rely on God's grace instead of his own efforts. The disciples, who give up everything, will rule with Jesus (Matthew 19:28), although not as soon as they think.

The next two sections show how difficult Jesus finds it to change the disciples' worldview. First, He will prophesy His death for the third time. In this case, Jesus specifically mentions He will be mocked, spit on, and flogged. In the very next story, James and John will ask Jesus for positions of great power and influence in His kingdom (Mark 10:35–45). Jesus denies their request, saying it is not for Him to decide. Jesus then reiterates that His followers are not those merely willing to face the same hardships He will face. Many will actually, literally face them, as in the case of James and John. James was killed by the sword at the order of Herod (Acts 12:1–2). Church tradition says that John was placed in a burning vat of oil and survived, then was exiled to the island of Patmos.

When Peter mentions that the disciples have left everything to follow Jesus, Jesus affirms the sacrifice even while He reminds the Twelve what is expected of them. Despite the rich young man's difficulty prioritizing God over his possessions, he seems to have understood Jesus' teaching in Mark 9:37. The man knows how to use his position of power to take care of people (Mark 10:19–20). The Twelve, on the other hand, are devoted to "a" messiah, but they seem to imagine this messiah as one who will give them worldly authority not unlike that which the rich young man already has. The suffering of the true Messiah, Jesus, and His mission to seek and save the lost (Luke 19:10) is not exactly what they expected. The disciples' god isn't money, it's power and influence. Ironically, God will give them their wishes (Acts 2), but by then they will know how to submit themselves and God's blessings back to God for the sake of the gospel.