Some Notes:

The English language has no gender-neutral pronouns. So when the words man, he, him, etc are used, they mean "Generic human being" unless the context specifically says otherwise. Only women get words devoted just to them.

Thou, Thee, and Thine are singular pronouns. You and Your are plural in the 16th Century English the King James Bible was translated into. This actually makes the message clearer than our habit of using "you" as both a singular and a plural.

In many scriptures I have changed the King James (English) spelling to American spelling (labour=labor, for example. I understand those in England still spell it with a u). Also, in some scriptures I have changed the "-eth" to a simple "s." Spelling standards weren't set in English until the mid 1800's, well after the translating of the KJV. So I see no problem with making these simple changes that don't affect the meaning of the scripture but make it easier for our modern mouths and ears to deal with.

Exodus 20- Commandment #3: Don't Take God's Name in Vain

7 Thou will not take the name of the I AM thy God in vain; for the I AM will not hold him guiltless (forgive) that takes His name in vain.

Deuteronomy 5:11 Thou shalt not take the name of the Lord thy God in vain: for the Lord will not hold him guiltless that takes His name in vain.  

Commandment 3

Some sins really are worse than others. Think about it; is stealing a grape from the grocery store really same as what Hitler did? No, of course not.

The worst sin of all is committing evil in God's name. This is the only sin that says God won't forgive.

I suspect this is what this verse is talking about: Matthew 12:32 "And whoever speaks a word against the Son of man, it shall be forgiven him: but whoever speaks against the Holy Ghost, it shall not be forgiven him, neither in this world, neither in the world to come."

Hebrew original: "Do not carry" the name of the Lord thy God in vain.

The NIV says "misuse the name of the Lord." This is committing evil in God's name, using God as an excuse to do wrong, to harm others.

When you misuse God's name by doing evil "for Him" you kill God; you kill His influence and reputation, condemning many other human beings to Hell.

An explosion in radical Atheism followed the 911 attacks, which were committed in Gods' name. This is the natural result of "taking the Lord's Name in vain."

This misrepresenting our God is the greatest possible evil.

“Vain” means empty or without meaning.

We are not to use the name of God idly and without meaning what we say, either.

It is easy to think of the common habit in our culture today to say “Oh gawd,” “G__ D__ It” “J_____C_____!” and so forth. These are most certainly using God’s name in vain. We don’t mean a thing by them and have no intention of calling on the All Mighty when we say them. It is disrespectful.

Imagine if your children, when angry or frustrated yelled your name out in the same way; not as a call for help but as a curse word. How much worse to do that to Our Lord?

This commandment also speaks of witnessing in court. We are not to lie in court at all because there is no way to administer justice if the witnesses lie. It’s just not possible.

In Psalm 139:20 David says, “They speak of you with evil intent; your adversaries misuse your name.” It distressed him for his God’s name to be misused. Does it distress us?

In Proverbs 30:9 Solomon begs God to make him middle class; “Otherwise, I may have too much and disown you and say, 'Who is the I AM?' Or I may become poor and steal, and so dishonor the name of my God.” He took honoring God and His name very seriously; much more than we do today.

God promises Israel, “I will come near to you to judgment; and I will be a swift witness against the sorcerers, and against the adulterers, and against false swearers, and against those that oppress the hireling in his wages, the widow, and the fatherless, and that turn aside the stranger from his right, and fear not Me, says the I AM of angels.” (Malachi 3:5) He equates “false swearers” with witches, adulterers, those that take advantage of the poor, widows and orphans. This is serious stuff!

Jesus addressed this issue, also. "Ye have heard that it has been said by" (or "to") "them of old time - Thou shall not forswear thyself, but shall perform unto the Lord thine oaths. But I say unto you - Swear not at all" (Matthew 5:33-34). This could be taken as “don’t curse, use profanity,” or “don’t make rash promises in the Name of the Lord.” Later He explains more;

“16 Woe to you, ye blind guides, which say, ‘Whoever shall swear by the temple, it is nothing; but whoever shall swear by the gold of the temple, he is a debtor!’

17 Ye fools and blind: for which is greater, the gold, or the temple that sanctifies the gold?

18 And, ‘Whoever shall swear by the altar, it is nothing; but whoever sweares by the gift that is upon it, he is guilty.’

19 Y e fools and blind: for which is greater, the gift, or the altar that sanctifies the gift?

20 Whoever then shall swear by the altar, swears by it, and by all things on it.

21 And whoever shall swear by the temple, swears by it, and by him that dwells in it.

22 And he that shall swear by heaven, swears by the throne of God, and by Him that sits on it.” Matthew 23:16

And James puts it plainly for us; “But above all things, my brethren, swear not, neither by heaven, neither by the earth, neither by any other oath: but let your yea be yea; and your nay, nay; lest ye fall into condemnation” James 5:12

We must at all times be careful that we only use the name of God respectfully and when we mean it. And we must make sure our speech, whether making promises or not, brings glory to Him. If we make promises, we MUST fulfill them.

But most of all, when we act in His name, we must make sure it is for good, it is in His true will, and not for evil.