Why does Exodus 20:2 say 'the Lord God' instead of just God?
Exodus 20:2 uses 'the Lord God' because it identifies Jehovah, the God intrinsically involved with Israel, whereas verse 1's 'God' is Elohim, the almighty God over all. This signals the law was given specifically to Israel though it exposes all the world's guilt.
Les teaches that Exodus 20:1 starts with 'God spake,' which is Elohim, the almighty God not just of Israel but of everything. Then verse 2 moves to 'the Lord God,' which is Jehovah God, who was intrinsically involved with the nation of Israel. Les explains this shows the law was specifically given to those under the law, yet Paul says all the world might be brought under its guilt. So the law was given to Israel, but it still has control over the whole human race.
I am the LORD thy God, which have brought thee out of the land of Egypt, out of the house of bondage.