"Again you have heard that it was said to those of old, 'You shall not swear falsely, but shall perform your oaths to the Lord.' But I say to you, do not swear at all: neither by heaven, for it is God's throne; nor by the earth, for it is His footstool; nor by Jerusalem, for it is the city of the great King. Nor shall you swear by your head, because you cannot make one hair white or black. But let your 'Yes' be 'Yes,' and your 'No,' 'No.' For whatever is more than these is from the evil one. Matthew 5:33-37
Matthew, chapter five, is largely about understanding the spirit of God’s law, rather than merely the letter of it. I pray we all understand by now that Jesus did not come to abolish the law (5:17-20). In fact, the spirit of the law makes the law stricter than does the letter.
Having compared the spirit and letter of the law regarding anger, lust, and divorce, Jesus turned to the subject of oaths. The word swearing in this passage does not refer to the use of profanity, but of oaths. What had been said, both in God’s Word and “to those of old,” is simple: (a) Do not swear an oath falsely, and (b) Fulfill the oaths you take. Simple, and presumably obvious.
Jesus raised the bar by saying, “do not take oaths at all.” Just say what you mean, mean what you say, and do as you said you would do. It is a shame, really, that we can say all sorts of things, with or without the least intention of honoring what we have said. Then, when we want someone to really believe us, we swear that we are telling the truth. Wouldn’t everyone be better off if our word was so reliable that there was no need to swear oaths? In other words: “Let your 'Yes' be 'Yes,' and your 'No,' 'No.'”
Jesus also addressed the fact that we commonly add all manner of provisions to our oaths. Jesus reminded His disciples of some of the silly variations in their day (v.34-36). In our day people say things like: “I swear on my mother’s grave,” and other absurd wordplays. This foolishness not only means we really mean it, but that we really, really mean it! Again how much better if we merely did as we say we would do?
One wise man said, “The more words a man uses to convince us that he is telling the truth, the more suspicious we should be that he is not.”
Does this mean that it is wrong, for example, to swear to tell the truth in court, or to make vows when entering into a marriage covenant? No, it does not. It is understood that in such particularly weighty and official circumstances, oaths are appropriate. Such oaths are a reminder to all parties involved that the unvarnished truth is expected and that there are consequences for defaulting on such oaths.
I particularly like Solomon’s word in Ecclesiastes regarding oaths:
Ecclesiastes 5:2-5 Do not be rash with your mouth, And let not your heart utter anything hastily before God. For God is in heaven, and you on earth; Therefore let your words be few. 3 For a dream comes through much activity, And a fool's voice is known by his many words. 4 When you make a vow to God, do not delay to pay it; For He has no pleasure in fools. Pay what you have vowed-- 5 Better not to vow than to vow and not pay.