The disciples have asked for understanding about the kingdom, and Jesus has given it in the form of parables, given and explained (1-50). Then Jesus asks if they understand these things, and they reply that they do (51). Of course, they don’t everything, but they do now understand more than they did before. Particularly, they now see - to their great blessing - what, or who is at the center of it all - Jesus himself (16). He himself is what all the Old Testament has been anticipating. And now a new era will dawn, building on the old, in him.
So when the disciples say that they do understand, Jesus replies:
Matthew 13:52 (ESV): “Therefore every scribe who has been trained for the kingdom of heaven is like a master of a house, who brings out of his treasure what is new and what is old.”
A note about two of the words. First, the role of a “scribe” in those days involved more than transcribing text from one paper to another. It also involved teaching. The roles of teacher and scribe had heavy overlap. Secondly, the word rendered “trained” here is, in the original language, the verb form of the word “disciple.”
Jesus is now talking to his disciples, whom he desires to spread his word, to teach. So he is sharing for us a crucial principle about what it means to be properly “discipled” for this task.
The order of logic in Jesus’ statement is crucial to understand. First comes the “discipling”, then comes the ability to bring out of one’s treasure - one’s heart - what is new and old. By “new” and “old”, Jesus must mean the old parts of the Bible, and God’s working in the world, as well as what will be new, in the new covenant. How to bring these things out of the storehouse, and then teach them to people - this depends on being “discipled” for the kingdom of heaven.
So then, what is this “discipling”, this “training”? Much of what we call discipling involves doing what folllows from being discipled in this verse. For us, discipleship begins with plumbing the storehouse of the Bible - learning the Old and the New.
But for Jesus, something must precede that: having one’s heart changed, in terms of its understanding of what it sees and its loyalties. The heart must come to see Jesus himself as the center and the point of everything, and the loyalties of one’s heart must therefore shift weight, onto him supremely. This “discipling” is what enables further understanding. Mastery of the “treasure” through study is enabled by the loyalties and loves of one’s heart being first “trained” on Jesus Christ.