Regarding the commandments of the Law, Moses told Israel, "Therefore keep and do them, because this is your+ wisdom and your+ understanding in the sight of the peoples who will hear all these statutes, and say, ‘Surely this great nation is a wise and understanding people.’" (Deut. 4:6)
That is why all Israel was given an additional requirement: "And these words which I command you today are to be on your heart, and you are to teach them diligently to your children..." (Deut. 6:6-7) All Israel is to think and meditate on what God has commanded, and understand it well enough to teach future generations.
Meditating on God’s Law enables us to see what God is seeking. Here’s a simple example. "When you build a new house, then you are to make a railing for your roof, that you may not bring guilt of bloodshed on your household if anyone falls from it." (Deut. 22:8)
Beyond the specifics about a house and a roof, this statute lays out a principle of personal liability. It is a practical example of what love of one’s neighbor entails. So far as your own property is concerned, you must act to insure your neighbor’s safety. Other statutes lay out the principle of compensation if you are negligent in that responsibility. (e.g. Ex. 21:19,22,36)
Murder is wrong because humanity was made in the image and likeness of God. (Gen. 9:6) If you meditate on that, you will be able to see what value the commandment is protecting. Every action that destroys that image and likeness of God in another is wrong.
Yeshua illustrated the fullness of that law, what it means when that law is written on the heart: "...Everyone who is angry with his brother without a cause will be guilty in the judgment. And whoever calls his brother, ‘Brainless!’ will be in danger of the Council. And whoever says, ‘Stupid fool!’ will be in danger of the fire of Gehinnom." (Mt. 5:22)
The connection between the purpose of a particular commandment or statute and the values it is protecting is not always obvious. For example, Yeshua went on to say, "Again you+ have heard that it was said to those of long ago, ‘You are not to make false vows, but are to perform your vows to the Everpresent Lord.’ But I tell you+, do not swear at all, not by heaven, for it is the throne of God; nor by the earth, for it is the footstool of His feet, nor by Yerushala’im, for it is the city of the great King. Nor should you swear by your head, for you cannot make one hair white or black. " (Mt. 5:33-36)
What is the relationship between "you cannot make one hair white or black" and "you are not to swear falsely"? If you make an oath to the Lord, you must do what you have vowed, but you do not control many things about yourself or about the world. You do not have the power to declare something and make it happen. So in order not to swear falsely, you had best "not swear at all".
If you take to heart the commandment given at Sinai, you will become aware of your own limitations. When you are truly aware of your own limitations, you will be content to let your "Yes" be "Yes," and your "No" be "No." You are not in control, God is.
For all those whose ancestors were brought out of Egypt by the Everpresent Lord, the role of God’s Law in the New Covenant is quite clear, even if the details require some meditation. The Law which God gave us at Sinai — "These words which I command you today are to be upon your heart." (Dt. 6:6]