The definition of the words oath, swear, pledge, and vow are all the same. They all mean to make a solemn promise about something. The person making a pledge is promising to do something in the future. If you think about this you will see that it is not possible to truthfully promise anything. I am not speaking of what a person intends to do, but what someone promises to do.
A solemn promise is not within the power of any man. No man can control the future, so no man can make a solemn promise in truth. When someone asks us to promise, or make a pledge, we should examine all of the situations which we think might cause us to break our promise and answer accordingly. However we do not even know the future. How then can we make a solemn promise and what promise that a Christian would make is not a solemn promise.
Let me illustrate what I am trying to say. Suppose you are walking down the street and you happen to meet a friend. Your friend stops you and explains that he desperately needs a loan. He asks for one hundred dollars. It seems like a lot of money, but you have a thousand in your pocket. However you intend to make a purchase with it and you do not want to go back to the bank, where you have more than a hundred thousand, in order to withdraw more. You fear you will miss out on the deal you had planed for. Your friend does not need the money until tomorrow so you promise to loan it to him in the morning. You see no reason that you can not fulfill your promise and it does seem reasonable, but it would be better to listen and contemplate what God says about making promises.
The ability to see the future is not given to man. Suppose you die tonight. Your friend who desperately needs the loan, which you promised, stopped searching for it, because of your promise. That is just one possible ending to the story. There are any number of possible endings.
You could forget, after all, the loan is not as important to you as it is to your friend. There could be a tornado, hurricane, or flood. Your bank could fail, or you could learn that you are bankrupt and did not realize it.
You are probably saying to yourself that these are very unusual occurrences and of course that is correct. This may lead you to think, because you could not predict these unusual circumstances that you have done nothing wrong. But do not forget your friend who depended on you to fulfill your promise. Your conscience will remind you that you have indeed erred.
Consider Matthew 5:33-37 (NIV), “Again, you have heard that it was said to the people long ago, ‘Do not break your oath, but keep the oaths you have made to the Lord.’ But I tell you, Do not swear at all: either by heaven, for it is God’s throne; or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King. And do not swear by your head, for you cannot make even one hair white or black. Simply let your ‘Yes’ be ‘Yes,’ and your ‘No,’ ‘No'; anything beyond this comes from the evil one.” Also James 5:12 (NIV), “Above all, my brothers, do not swear‑‑not by heaven or by earth or by anything else. Let your “Yes” be yes, and your “No,” no, or you will be condemned.”
While you are contemplating solemn promises and you still think you are released from your promise if unusual circumstances cause you to fail to fulfill your obligations. Consider Leviticus 5:4 (NIV), “Or if a person thoughtlessly takes an oath to do anything, whether good or evil‑‑in any matter one might carelessly swear about‑‑even though he is unaware of it, in any case when he learns of it he will be guilty.” Did God give you an out? He said anything, good or evil, in any matter, even if you are unaware of it you will be guilty.
I do not see any possible way to justify a broken promise. If you are one of those who would say Leviticus is the Old Testament and it no longer applies to the events of today you are wrong. It is true that the penalty for sin has been paid for all those who will admit guilt, and plead for mercy, but it is still wrong to sin.
Only God knows the future, so only God can make a promise. If we promise to do anything without the ability to fulfill it we are lying, and we do not have the ability to control or predict the future, so any promise is basically only a lie.
If you are inclined to think your motives make a vow, or pledge right then consider Jephthah the Gileadite who made a vow to the Lord. His motives were right. However he did not know the future and he had to sacrifice his only daughter, because of his vow.
Satan can not change the Word of God, so he changes the meaning of the words in which the Word of God is written. This is how Satan has confused this issue. Satan has managed to shade the meaning of swear into meaning using God’s name in vane. It does not mean that when it is used in the Bible. It means to make a promise. When we make a promise we are setting ourselves up as a God. We, though we do not mean to, are indicating that we can do what only God can do. Do as the Bible says (Mat. 5:34-37 NIV), “But I tell you, Do not swear at all: either by heaven, for it is God’s throne; or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King. And do not swear by your head, for you cannot make even one hair white or black. Simply let your ‘Yes’ be ‘Yes,’ and your ‘No,’ ‘No'; anything beyond this comes from the evil one.”
That is how promises, oaths, swearing, pledges, and vows look to me.