You shall not take the name of the LORD your God in vain; for the LORD will not hold him guiltless that takes his name in vain.
Read Chapter 20
Augustine of Hippo
AD 430
You are told “Do not take the name of the Lord your God in vain”; do not regard Christ as a creature because for your sake he put on the creature. And you, you despise him who is equal to the Father and one with the Father.
The second commandment: “You shall not take the name of the Lord your God in vain; for whoever takes the name of the Lord his God in vain will not be purified.” The name of the Lord our God Jesus Christ is Truth: he himself said, “I am the truth.” So truth purifies; futility defiles. And because whoever speaks the truth speaks from what is God’s—for “whoever speaks falsehood speaks from what is his own”— to speak the truth is to speak reasonably, whereas to speak futility is to make a noise rather than to speak. Rightly, because the second commandment means love of the truth, the opposite of that is love of futility.
Here too the Lord himself teaches in the passage before us about another Lord. For he says, “I am the Lord thy God,” and adds, “You shall not take the name of the Lord your God in vain.” The second Lord is here mystically instructing his servant about the Father, that is to say, the God of the universe. And you could find many other similar instances occurring in Holy Scripture, in which God speaks as if in a second voice about another. The Lord himself speaks as if about another. .