Most of us know the command from the Decalogue: "You shall not take the name of the LORD your God in vain, for the LORD will not hold him guiltless who takes His name in vain." (Exo 20:7) Yeah, we know. We're not to say the word "God" as a vain or frivolous word. You know, like a swear word or something. Well, of course, that would include "Jesus", too. We get it. Do we?
"The name of the Lord" is actually a foreign phrase to modern America. It wasn't as unclear in former times. Back when people understood authority far better than we do today in our "individualism" and "question authority" days, they understood that there were those in authority who were to be obeyed -- a different class, a different echelon of people. Kings, masters, rulers, these people needed to be obeyed because these people had authority. In addition to these people, the underlings would need to obey those who came "in the name of the king". That is, an authority had the right to assign some of that authority to one of his people, and those under that authority would need to submit to this person operating "in the name of the king" as if the king himself was there, not because of the name, but because of the king. "The name", in these times, represented the person. You've heard, I'm sure, someone concerned about "my good name". It refers to their character, their reputation, much more than the term with which you address them.
We see this in Scripture. Jesus said, "I have come in my Father's name." (John 5:34) That's not a term, but a character reference. He wasn't saying, "Please address me as 'the Father'." He was saying, "I have come under the authority of and in the character of the Father." Jesus promised "If you ask me anything in My name, I will do it." (John 14:14) That's not "if you tack on 'in Jesus' name'." It is "under My authority and according to My character".
I think we get this. I think it's clear that there is nothing magical about "in Jesus' name, amen" in our prayers. I'm fairly sure, if we think about it, we know that "in My name" is not a mere reference to a term, but a reference to the character and authority of Christ. Now, if that is true, what about that command in the Ten Commandments? What does it mean to "take the name of the LORD your God in vain"? It means that we are not allowed to claim for yourself the character and authority of God vainly. Sure, that would include using God's name as a swear word, but that is only the start of it. It would include the lack of the proper reverence and respect for a holy God. It would include claiming to be a Christ-follower while not following Christ. It would include worshiping God with your lips while being far from Him in your heart. It would include attitudes and actions that bring shame upon His name while we are claiming His name for ourselves.
Most of us accept the Ten Commandments as valid moral instructions for modern Christians. If this is true, then "You shall not take the name of the LORD your God in vain" is one of those still-valid commandments. If this is true, perhaps we ought to be more diligent in this regard. Are you carrying around the name "Christian" without a thought of how your life reflects on Christ? Are you a "God-fearer" who has little fear of God? Maybe you manage to avoid saying God's name in a frivolous or crude way. Do you live as if your relationship with God is of little value? That's what it means to take the name of the Lord in vain.