Deuteronomy 4:6 Keep therefore and do them; for this is your wisdom and your understanding in the sight of the nations, which shall hear all these statutes, and say, Surely this great nation is a wise and understanding people.
The right response to God’s great grace and salvation is to keep the Commandments of God revealed through Moses. Because the Lord set you free from bondage in Egypt (sin and the world), therefore you will keep and do my Commandments and all the laws of Moses. The motivation and the power to live accordingly is the Gospel of Salvation.
When God’s people respond by living such a wise and understanding lifestyle, the the world will take notice. Thus you become God’s witnesses. Jesus puts it this way in Matthew 5: “Let your light shine before others, so that they may see your good works and give glory to your Father.” The Bible says the Christian Church is a peculiar people, meaning their good works lifestyle is so different from the world’s. Indeed, they will say, “See how they love one another.”
Do we live such a distinguishable life? Yes and no, because we are at the same time saint and sinner. But Jesus, out of love, lived such a holy life for us, completely. We believe Him and so we live in Him.