The task of man's earthly life is preparing himself for eternal salvation and beatitude. To attain this, a man must live in a holy and pure manner - that is, according to God's will.
How can one recognize this will of God? First of all, in one's conscience, which for this reason, is called God's voice in the soul of man. If the fall had not darkened the human soul, man would be able unerringly and firmly to direct the path of his life according to the dictates of his conscience, in which the inner moral law is expressed. We know, however, that in a sinful man, not only are the mind, heart and will damaged, but the conscience is also darkened and its judgment and voice have lost their firm clearness and strength. It is not without reason that some people are called unconscionable.
Therefore, conscience alone - the inner voice - became insufficient for man to live and act according to God's will. The need arose for an external guide, for a God-revealed law. Such a law was given by God to people in two aspects: first, the preparatory - the Old Testament law of Moses - then the full and perfect Gospel law.
There are two distinguishable parts in Moses' law: the religious-moral and the national-ceremonial which was closely tied with the history and way of life of the Jewish nation. The second aspect is gone into the past for Christians, that is, the national-ceremonial rules and laws, but the religious-moral laws preserve their force in Christianity. Therefore, all the ten commandments in the law of Moses are obligatory for Christians. Christianity has not altered them. On the contrary, Christianity has taught people to understand these commandments, not externally - literalistically, in the manner of blind, slavish obedience, and external fulfillment, but it has revealed the full spirit and taught the perfect and full understanding and fulfillment of them. For Christians, however, Moses' law has significance only because its central commandments (the ten which deal with love of God and neighbors) are accepted and shown forth by Christianity. We are guided in our life not by this preparatory and temporary law of Moses, but by the perfect and eternal law of Christ. St Basil the Great says, "If one who lights a lamp before himself in broad daylight seems strange, then how much stranger is one who remains in the shadow of the law of the Old Testament when the Gospel is being preached." The main distinction of the New Testament law from that of the Old Testament consists in that the Old Testament law looked at the exterior actions of man, while the New Testament law looks at the heart of man, at his inner motives. Under the Old Testament law, man submitted himself to God as a slave to his master, but under the New Testament, he strives toward submitting to Him as a son submits to a beloved father.
There is a tendency to regard the Old Testament law incorrectly. Some see no good in it, but only seek out features of coarseness and cruelty. This is a mistaken view. It is necessary to take into consideration the low level of spiritual development at which man then stood thousands of years ago. Under the conditions of the times, with truly coarse and cruel morals, those rules and norms of Moses' law which now seem cruel to us (e.g., "an eye for an eye, a tooth for a tooth," etc.) in reality were not such. They did not, of course, destroy human cruelty and vengeance (only the Gospel could do this), but they did restrain it and establish firm and strict limits upon it. Moreover, it must be remembered that those commandments about love toward God and neighbors, which the Lord indicated as the most important, are taken directly from the law of Moses (Mk. 12:29-31). The Holy Apostle Paul says of this law, "The law, therefore, is holy and each commandment is holy, just and good" (Rom. 7:12).
On the Law of God, by Metropolitan Philaret (Voskresensky)
Translated by Hieromonk Varlaam Novakshonoff