Exodus 20:7

As a child, I thought the 10 Commandments were simply a set of rules to follow. Then, I discovered I couldn't keep the rules, leading me to Christ for my righteousness. Then, the 10 Commandments no longer condemn, but show us the character of God. As a believer, I can look to these laws to see how to please the Father. For if Christ never once violated these laws, and my desire is to look more like Him, then these laws help me know Him.

You shall not take the name of the Lord your God in vain, for the Lord will not leave him unpunished who takes His name in vain.

Many people mock God's standard regarding blasphemy. They try to paint a picture of a weak, hyper-sensitive God who gets His feelings hurt by mean words. But within this command, God reminds us He will not leave a blasphemer unpunished. Perhaps no other commandment reveals the extreme depravity of man. God gives us life, breath, relationships, and the offer of His Son, and we respond using His name as an expletive. This sin that so many want to dismiss is one of the clearest exposures of our sinful hearts. Once this depravity is exposed, we should take great effort to only use divine names with a desire to glorify God. (We should also rid ourselves of names that come close.) Jesus says

Where two or three have gathered together in My name, I am there in their midst.

What does this have to do with blasphemy? Consider the phrase "in My name." To speak in a person's name means we speak with their authority. His name is not a postage stamp. I can not just paste it onto the end of my prayer to ensure that it arrives to God. To do anything (pray, witness, act, speak) in His name means that I am doing it in His authority. How can I, a sinful, ignorant man, do anything with the authority of Chirst? The context reveals how. If I speak the words of Christ, in a manner consistent with Christ, I am speaking with His authority. Any business person has seen this played out. If management informs us that "corporate" is issuing a new policy, it comes with the authority of the corporation, even though it wasn't delivered by the president. Why? Because we understand that it was corporates words, presented to us in a consistent fashion, and that our obedience is now required. For me to speak, I may not claim the authority of Christ unless I am speaking His words, in the way He desires. That's the only reason a church even has the authority to discipline. The church has no authority except that which has come from Christ.

In one way, this is why I get very nervous when I hear people claim a revelation from God outside of His Word. If they are wrong, they are attributing something to God that is not His (thus using His name in vain). That was the great sin of the false prophet. It wasn't that they made a bad prediction, it is that they credited God with their "vision" and are therefore using God's name where it doesn't belong. But even for us cessationists, blasphemy can be a real possibility. Do we enforce standards that the Scriptures do not? Do we endorse actions that the Scriptures forbid? Do we do either with an attitude contray to that which honors Christ? Perhaps, this is why James says:

Let not many of you become teachers, my brethren, knowing that as such we will incur a stricter judgment. For we all stumble in many ways. If anyone does not stumble in what he says, he is a perfect man, able to bridle the whole body as well.

Every word that comes from our mouth is capable of blasphemy, not just our expletives.