I was in the 1st grade the first time I ever got in trouble in school. I was excited to find out my teacher Mrs. Gunden had a real, human first name. We were sitting in our small reading groups, and I was learning to sound out letters to make words. Our teacher had to go to the office, and as she walked out the door, I said, "Bye, Julie."
The whole classroom froze in suspended animation. Audible gasps of horror filled the air as Mrs. Gunden stopped dead in her tracks. I couldn't breathe. She turned around and with a glare in her eyes that could have melted the armies of the antichrist, she said, "Who said that?" I was immediately betrayed by dozens of finger-pointing cowards who were still gawking with their mouths hanging wide open.
I did not have the right to know her personally. This lesson about honor and respect stuck with me.
The third commandment is "Do not take the name of the Lord your God in vain." Many people make the mistake of thinking this is a commandment about cussing. It sort of is but mostly is not. This command, unlike the previous two, was written in the 3rd person, and God reveals his name to us: Yahweh (Lord). Modern translations miss the original intent of the word "take" which means "to carry", so when we understand this commandment more completely, it really means "You shall not carry the name of Yahweh in an empty way."
We often refer to God by his titles: God, Creator, etc. But God revealed himself to his people by name: Yahweh. To his people, his name is given in the familiar. Jesus called him Abba (Father). God reveals his name to us so we can know him personally. This commandment is about trying to carry his name without really knowing him at all.
None of us like to be taken for granted, do we? This is probably especially true if you are the creator of the universe and sustainer of all life. We can become flippantly familiar with God and approach him with a flippant disregard for who he is, like when his name rolls of our tongue as if it doesn't really matter or if we claim his name and then live like it doesn't matter.
We can misuse the name of the Lord when we use it cheaply (cursing, swearing oaths, making promises, damning, etc). But we can also misuse the name of the Lord when we misrepresent who he is (by disregarding his counsel, damaging others in his name, or embracing false teaching).
This is another command about the affection of the human heart. God does not want to be taken for granted but carried with significance in our lives as we walk in this world. In these first three commandments, he is reminding us what loving him looks like: 1] no other gods, 2] don't worship created things, and 3] don't treat your relationship with me casually or flippantly.
It's so much more than just watching your mouth.