THE GOSPEL OF JESUS CHRIST
God is holy and perfect, and He requires holiness and perfection from us. Holiness is the inability to sin. It means moral perfection, and it is something that God alone possesses. Holiness is an attribute of God's perfect nature. Therefore, since there is no one greater than God and God is the greatest good, God is necessarily the standard of what is good.
The Law is a reflection of the character of God. The reason it is wrong to lie, cheat, and steal, etc., is that God cannot do these things. Because He is holy, He is incapable of lying, cheating, etc. Therefore, the Law becomes the standard of righteousness. But we are incapable of keeping the Law because we are not holy. We are sinners. Once this is said, you must ask the person if he has ever sinned. You might want to explain that sin is breaking the Law of God. You ask the person if he has ever lied, cheated, stolen, or been angry unrighteously, etc. He will answer "yes" to one or all of these and that is when you tell him that he has broken God's Law and is a sinner. Furthermore, there is no law that has no punishment. A law without punishment is a slogan. The punishment for breaking God's Law is eternal damnation.
The Gospel is the good news that the judgment of God upon the person who has broken God's Law can be removed in the person of Jesus. This is done because Jesus, who is God the Son in flesh, was able to perfectly live the Law and offer a sacrifice to God the Father. His sacrifice is the death on the cross, which was the payment for the penalty of breaking the Law of God. He died there and three days later physically rose from the dead as proof that His words, deeds, and sacrifice were true. Therefore, if anyone wants to escape the righteous judgment of God, he must receive the sacrifice that Christ made on the cross. This is done by faith, by asking Jesus to forgive you of your sins.