Answer: The preface to the Ten Commandments is contained in these words, I am the Lord thy God, which have brought thee out of the land of Egypt, out of the house of bondage.₁ Wherein God manifests his sovereignty, as being JEHOVAH, the eternal, immutable, and almighty God₂; having his being in and of himself₃, and giving being to all his words₄ and works₅ and that he is a God in covenant, as with Israel of old, so with all his people₆; who, as he brought them out of their bondage in Egypt, so he delivers us from our spiritual thraldom₇; and that therefore we are bound to take him for our God alone, and to keep all his commandments.₈

1. Exodus 20:2 : The Preface to the Ten Commandments
2. Isaiah 44:6
3. Exodus 3:14
4. Exodus 6:3
5. Acts 17:24; Acts 17:28
6. Genesis 17:7; cf. Romans 3:29
7. Luke 1:74-75
8. 1 Peter 1:15-18; Leviticus 18:30; Leviticus 19:37

For further study see:

1. Q43. What is the preface to the Ten Commandments?
2. Dr. R.C.Sproul explains the aseity of God (i.e God’s eternality and self-existence)