The NLT translates this verse as "A man who makes a vow to the LORD or makes a pledge under oath must never break it. He must do exactly what he said he would do." As a kid, my father often told me "A man is only as good as his word." He seemed especially fond of that saying when he knew I was not entirely truthful with him. At the time, I thought that was just my Dad. Little did I realize, he was giving me God's instruction in his way.
I have never been a witness in a trial, but I have seen many on television. They would swear the witness in with the question "Do you swear to tell the truth, the whole truth and nothing but the truth, so help you, God?". I don't know if they use that language anymore or not, but I sure don't hear it on television.
God has a lot to say about the promises, vows, and oaths we make, especially when we reference His name in our commitment. The most common use of a vow is in a marriage ceremony. A man and woman vow before God to keep the promises they are making to each other. In effect, they are calling upon God as a witness to their commitment. Hebrews 4:13 says God is the final judge, "And no creature is hidden from his sight, but all are naked and exposed to the eyes of him to whom we must all give account." He is the one to whom we will ultimately answer for the promises we make. Knowing that should strengthen our resolve to keep our commitments.
As believers, we should be so committed to the truth that a simple yes or no is sufficient. James 5:12 says it this way, "But above all, my brothers, do not swear, either by heaven or by earth or by any other oath, but let your "yes" be yes and your "no" be no, so that you may not fall under condemnation." We should not be surprised at the simplicity with which James handles how we speak. Don't we worship and serve a God who does exactly what He says? He is the True Promise Keeper.
Father, as a child of Yours, I want my word to be as sure as Yours, but I know it is not. Thoughtless utterance is a good description of how I speak sometimes. Holy Spirit, quickly convict me when I start down a path that leads to a promise I know I can't fulfill, or to make a commitment and then willfully to forget. May a simple yes or no suffice for me. I desire to speak the truth in love whatever the situation.