I am, the Lord your God - The frequent repetition of this formula in these parts of the Law may be intended to keep the Israelites in mind of their covenant with Yahweh in connection with the common affairs of life, in which they might be tempted to look at legal restrictions in a mere secular light.
Related Commentaries of Leviticus 18:2
Leviticus 18:2
2 Speak unto the children of Israel, and say unto them, I am the LORD your God.