Matthew 19:30 - Ellicott's Commentary On The Whole Bible

Many that are first shall be last. — The words point obviously not only to the general fact of the ultimate reversal of human judgments, but to the individual case of which the disciples had made themselves the judges. They had seen one who stood high in his own estimate brought low by the test of the divine Teacher. They were flattering themselves that they, who had left all, and so could stand that test, were among the first in the hierarchy of the kingdom. For them too, unless their spirit should become other than it was in its self-seeking and its self-complacence, there might be an unexpected change of position, and the first might become the last. The parable that follows was designed to bring that truth more vividly before them.