By Fr. Seraphim Slobodskoy
Genuine good Christian life may be led only by those who have faith in Christ and who strive to live by this faith; that is, those who by their good works fulfill the will of God. Good works are an expression of our love, and love is the foundation of all Christian life. God is love; and he that dwelleth in love dwelleth in God, and God in him (John 4:16). For God so loved the world, that He gave His only begotten Son, that whosoever believeth in Him should not perish, but have everlasting life (John 3:16). Thus God by this act revealed His love to mankind.
Love which is not accompanied by good works is not true love, but is merely lip service. That is why the Word of God says, Faith without works is dead (James 2:20). The Lord Jesus Christ Himself said, Not every one that saith unto Me, Lord, Lord, shall enter into the Kingdom of Heaven (Matt. 7:21). For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them (Eph. 2:10).
Furthermore we have received from God special means for discerning good deeds from evil. The means are the internal law of God, or conscience, and the external law of God, or the His commandments of God.
The word conscience denotes the internal, spiritual strength of a man, or the manifestation of the soul of a man. The conscience, as the internal law of God ("voice of God"), is present in every person.
The conscience is the internal voice which tells us what is good and what is evil, what is proper and what is improper, what is righteous and what is not. The voice of the conscience obligates us to do good and to shun evil. For every thing good the conscience rewards us with internal peace and calm. For everything wrong, incorrect, improper, or evil, the conscience judges and punishes so that a person acting against the conscience feels himself in moral discord, tormented by pangs of conscience.
But the conscience, as the spiritual strength of a man, requires development and improvement along with the other spiritual faculties of a man, namely, with his mind, heart, and will. The mind, heart, and will of man have become darkened from the time of Adam and Eve. From that time the voice of conscience has been shown to be weak and insufficient as a manifestation of spiritual strength. If man does not develop spiritual strength in himself, then the internal voice of conscience in man falls asleep by degrees and dies, as in a "man without conscience."
From this it is clear that the internal law of conscience alone is not enough for man. Even in Paradise God revealed His will to the first people. It follows that in order to exist in an innocent, righteous state, it is necessary for a man to have the external law from God. Even more so is it needed as a result of the fall from Grace.
In order that man would always remain in "fear of his conscience," the Lord God gave us the external law, the commandments of God.
This law was given in its simplest form in Old Testament times, when Moses received the Law on Mount Sinai. The most important Ten Commandments were written on two stone tablets. These commandments were made more profound and lofty in the Saviour’s Sermon on the Mount, in His nine points known as the Beatitudes. But the Lord also confirmed that the Old Testament Ten Commandments were to be known and fulfilled.
The Saviour said, Think not that I am come to destroy the Law, or the prophets: lam not come to destroy but to fulfill (Matt. 5:17).
When a young man asked, Good Master, what good thing shall I do, that I may have eternal life? — the Lord answered right away, // thou wilt enter into life, keep the commandments (Matt. 19:16-17).
However, the Lord taught that these commandments, according to His interpretation, must be kept to a high degree of perfection. Thus, the Lord Jesus Christ suggests that believers should not only shun transgression of the Law, but should not even think about it or desire it, thus requiring from them a more clean heart.
(from: The Law of God by Fr. Seraphim Slobodskoy)