Good words from responsible and insightful biblical theologian, Thomas Schreiner:
“Jesus concluded the parables in Matt. 13 by comparing the kingdom of heaven to a scribe ‘who brings out of his treasure what is new and what is old’ (Matt. 13:52). Jesus considered here the OT, the many prophecies about the kingdom of God. The disciple of Jesus, however, must interpret the prophecies in light of what is new, the dawning of the kingdom of God in the ministry of Jesus. The wise disciple, then, both grasps the meaning of the OT prophecy and discerns its fulfillment in Jesus. The new and the old are rightly related and correlated to one another. The old is not imposed upon the new, nor does the new squelch the old. Both the new and the old have their proper place, but the old, ultimately and finally, can be grasped only by those who understand the newness present in Jesus.”
From New Testament Theology: Magnifying God in Christ (p. 64).