During the infancy of God’s people, the law was their guardian (paidagogos or child-leader, Galatians 3:25). But in this age of spiritual maturity, we are no longer under a child-leader. Borrowing from the picture drawn by Galatians 3 and 4, think about a person’s progress though life.
As a youngster, he is under the rules of his childhood schools. While there, how should he show proper respect? By appreciating his teachers and obeying their rules. That is exactly what we see in the Sermon on the Mount.
Whoever relaxes one of the least of these commandments [of the Law] and teaches others to do the same will be called least in the kingdom of heaven, but whoever does them and teaches them will be called great in the kingdom of heaven. (Matthew 5:19)
Jesus practiced complete obedience to the Law of Moses. In Matthew 5, He taught His fellow-Jews to do the same. Why? Because, back then, that was the covenant they were under. Jesus had not yet died. Therefore, the law was still in effect. It deserved full obedience in every detail.
As the child grows, he completes his early schooling. He is ready for the next level of education. But suppose that he chooses to re-enter his old elementary school. He sits in a chair too small for him. He plays with little toys. He keeps the school’s rules made for small children. Imagine the reaction of his former teachers. They would be puzzled, and then outraged. They did not train him to act like a child forever. If he truly wishes to honor them, he should do so by benefiting from their preparation and moving forward in life.
As a young adult, this person goes to university. After graduation, he finds employment. The university has rules and policies, and so does his employer. In both cases, the new rules treat him as an adult. He respects the authorities over him. Does this new respect mean he no longer respects former teachers? Actually, he respects his childhood teachers all the more. Now, he sees how the early foundation they laid has served him well, all along the way. He benefits, not by keeping rules designed for infants, but by applying the enduring lessons and principles that brought him to maturity.