33"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.' 34But I say to you, do not swear at all: neither by heaven, for it is God's throne; 35nor by the earth, for it is His footstool; nor by Jerusalem, for it is the city of the great King. 36Nor shall you swear by your head, because you cannot make one hair white or black. 37But let your "Yes' be "Yes,' and your "No,' "No.' For whatever is more than these is from the evil one.
Footnotes in my Bible say they had all kinds of regulations regarding vow taking, but only the ones sworn to God were binding. The second commandment says "You shall not take the name of the Lord your God in vain". Is this where they got their basis for the regulations regarding vow taking, that swearing to God is more binding so you aren't using the Lord's name in vain? But Jesus says we shouldn't swear at all. What you say should be just as binding as if someone had you swear to it. If there are times that you feel you must swear to something, it is an indication that you don't see your word as binding, that you don't always tell the truth, or that you feel you don't normally have to follow through with what you say. This is simply opening the doorway for the devil to do his evil work.
Other than swearing to the Lord, the examples Jesus uses here: swearing by heaven, earth, Jerusalem, or by your head may seem a little weird to us. I believe these are just common vows of the time. Today you hear more of: "I promise", "I cross my heart and hope to die", "I swear on my Mother's grave", etc. These things, just as in Jesus' example, all belong to God, not us. Even your body belongs to God. Even the hairs on your head belong to God. Sure you can cover your hair color with dye, but you cannot control the natural color of your hair. Nothing is yours to swear away. So not only should swearing not be needed, but we really have nothing of ours to swear by.
Jesus makes many promises to us. But notice in His promises, He never uses any words to swear His promise. He doesn't say "I promise", or "I swear", or "I vow". What I have heard Him say over and over again is "Assuredly I say to you..." He is telling us that He definitely said this thing. What He says is the truth and He follows through with what He says. There is no need for Him to swear a promise, we just need to know that it is something He said. Let your "Yes" be "Yes" and your "No" be "No". We should follow His example and always follow through with what we say too.