Question: "What does it mean to let your yes be yes and your no be no?"
Answer: Jesus said, “Let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil” (Matthew 5:37, KJV). The NIV clarifies the meaning of Jesus’ words somewhat: “All you need to say is simply ‘Yes’ or ‘No’; anything beyond this comes from the evil one.” The context of this verse has to do with oath-keeping. We’ll take a look at the broader context of Jesus’ sermon:
Matthew 5 is part of the Sermon on the Mount. In this section, Jesus addresses some of the underlying principles of certain Old Testament laws. There are some cases in which a person could obey the letter of the law but still be guilty of breaking the principle. The Pharisees and teachers were experts at keeping the letter of the law, but Jesus warns His hearers that, unless their righteousness surpasses that of the Pharisees and teachers of the law, they will never enter the kingdom of heaven (Matthew 5:20). This statement would have shocked His hearers, because the Pharisees and scribes were looked up to as paragons of obedience. Jesus points out that technical obedience is not enough if the spirit of the law is broken.
In Matthew 5:21–22, Jesus teaches that it is not enough to be “technically” innocent of murder because one can have murderous thoughts and attitudes without carrying out the physical act. In Matthew 5:27–28, Jesus says it is not enough to be “technically” innocent of adultery because a lustful look destroys one’s purity of thought. In Matthew 5:31–32, Jesus teaches that divorcing a wife for an inadequate reason, even when the “proper paperwork” is filed, may not be a legitimate divorce in God’s eyes.
In Matthew 5:33–37, following the same pattern, Jesus addresses the subject of telling the truth. Jesus tells the crowd not to break their oaths. An oath was a promise to do or not do something, invoking God as witness and the One to bring judgment if the promise was broken. It was common for people to make oaths to emphasize their seriousness and truthfulness. Sometimes they would swear on something less than God, such as “heaven.” The point of the lesser oath was to allow some flexibility in breaking the oath—since God’s name had not been invoked, they reasoned, breaking the oath wasn’t that bad. In this case, the oath was being made by a person who was not afraid to break it, making the oath duplicitous. Instead of varying the “sincerity level” of oaths, Jesus says to simply say “Yes” or “No” and mean it. The invocation of God’s name is a mere technicality. Mouthing a meaningless oath does not create loopholes for yourself. Your word should be your promise. Jesus says that, oath or no oath, simply say what you mean and stick by it.
Here is the whole context: “You have also heard that our ancestors were told, ‘You must not break your vows; you must carry out the vows you make to the Lord.’ But I say, do not make any vows! Do not say, ‘By heaven!’ because heaven is God’s throne. And do not say, ‘By the earth!’ because the earth is his footstool. And do not say, ‘By Jerusalem!’ for Jerusalem is the city of the great King. Do not even say, ‘By my head!’ for you can’t turn one hair white or black. Just say a simple, ‘Yes, I will,’ or ‘No, I won’t.’ Anything beyond this is from the evil one” (Mathew 5:33–37, NLT).
In Matthew 5:34, Jesus says, “Do not swear an oath at all.” Some have interpreted this to mean that a Christian should never take an oath for any reason, such as testifying in court. A witness is “sworn in” raising his or her right hand (and sometimes placing the other hand on a Bible) and promising to “tell the truth, the whole truth, and nothing but the truth.” However, the point of Jesus’ teaching is not that taking an oath in this manner is wrong. Taking a meaningless oath in order to create a loophole and retain the option of breaking it is wrong. If an oath is required in the course of civic duty, the Christian should have no problem making it. The proper application of Jesus’ principle of “let your yes be yes” is that the Christian must be truthful in all circumstances.