The last shall be first (and the first last)

This saying appears in the Bible, in 3 gospels: Matthew 20:16, Mark 10:31, and Luke 13:30.

In each case it refers to judgments being made, about priorities, that might seem paradoxical or unfair. In the first case it refers to the way vineyard workers are paid relative to the amount of work they did, and in the other two cases to people's priority in getting into heaven relative to their good works during their lifetime. What the saying means is roughly "It is not your place to criticize or dispute the judgments made by your earthly masters, or by God."