Hi gallenwalsh,
This excerpt from the article 'the Sermon on the Mount...' give a good explanation about vows and oaths.
http://bible-truths.com/lake16-D3.htm -------------------------
[4] "Again you have heard that it has been said by them of old time, You shall not forswear yourself, but shall perform unto the Lord your oaths" (Matt. 5:33). Now this one I thought for sure was doing away with the old and contradicting the old, when Jesus said, "But I say unto you, Swear NOT AT ALL... but let your communication be, Yea, yea: and Nay, nay: for whatsoever is more than these comes of evil" (Vers 34-37).
Under Moses Israel was allowed to swear by God's name only: "You shall fear the LORD thy God; him shall thou serve, and to him shall thou cleave, and swear by His name" (Deut. 10:20).
They could not swear in the name of any other gods: "...neither make mention of the name of their gods, nor cause to swear by them, neither serve them, nor bow yourselves unto them" (Jos. 23:7).
One could swear only by the Name of God, and never falsely: "And ye shall not swear by My name falsely, neither shall thou profane the name of thy God: I am the LORD" (Lev. 19:12).
Pay attention to the words. The first "you have heard" statement has absolutely nothing to do with whether one should swear or not swear. It has to do with lying to God. Let's read it again: "You shall not forswear [Gk; opiorkeo-'swear falsely or commit perjury' ], but shall perform [Gk: apodidomi 'deliver, pay, render' ], unto the Lord your oaths." Moses said that anyone who swore, had to perform what they swore, and not lie or perjure themselves: "That which is gone out of your lips you shall keep and perform..." (Deut. 23:23).
Again, "And you shall not swear by My name falsely..." (Lev.19:12).
And again: "If a man vow a vow unto the LORD, or swear an oath to bind his soul with a bond; he shall not break his word, he shall do according to all that proceeds out of his mouth" (Num. 30:2). But notice the word "IF." It was not a commandment that all men and all women MUST SWEAR. Even an unconditional vow IS an oath (swearing), see Vine's Concise Dictionary of Bible Words. But, notice that swearing oaths are not requirements of God for all to do:
"When you shall vow a vow unto the Lord your God, you shall not slack to PAY IT... But if you shall forbear [abstain] to vow, it shall be NO SIN IN YOU" (Deut. 23:21-22).
Failing to uphold one's oath or vow was the very sin that Ananias and Sepphira committed before Peter. They "said" that they would give the price of a parcel of land to the Apostles. But after they sold it they "kept back part of the price." They did NOT "perform unto the lord their oath." And for this God killed them-their "whole body shall be cast into hell [Gehenna]" in the day of Judgment, because of this sin of "lying to the Holy Spirit." (Acts 5:1-11). They didn't need to vow in the first place. Had they simple sold their property (without first making a great swelling gesture of benevolence before the apostles), and given part of the proceeds to the apostles, nothing more would have happened.
Here is a perfect example of how "But I say unto you, 'Swear not at all'" would have saved their lives.
Notice what Peter told Ananias:
"While it remained, was it not your own? And after it was sold, was it not in your own power? Why have you conceived this thing in your heart? [why did you make an oath?] you have not lied unto men, but unto God" (Verse 4).
In other words, If you had not sworn before men that you will give this gift to God, you would not be held accountable for that oath. Now you are accountable. Now they shall die for lying to God. So, "don't swear at all," and you will not perjure yourself, should you not be able to deliver on your promise.
Why did Jesus instruct them to not swear by "heaven, earth, Jerusalem, by your head?" Because these are all things that the Scribes and Pharisees swore by, and the disciples were steeped in the false religion of these leaders. As the Pharisees knew from experience that they often could not follow through on their oaths to God, they started to swear by things other than "God's Name." They started to swear by things only somewhat related to God, so that when they broke their word they could claim that they never did "swear by MY name."
Jesus sharply rebuked them for such nonsense in Matt. 23:16-23 where they swore by, the temple, the gold, the altar, the altar gifts, heaven, etc."
Peter swore before Jesus: "Peter said unto Him, Though I should DIE with Thee, yet will I not deny Thee. "Likewise said also ALL THE DISCIPLES" (Matt. 26:36). They ALL SWORE. A few hours later Peter swore again: "Then began he [Peter] to CURSE AND TO SWEAR, saying, I know NOT THE MAN..." (Matt. 26:74) "Then ALL THE DISCIPLES FORSOOK HIM, and fled" (Ver. 56).
No wonder James later wrote: "But above all things, my brethren, SWEAR NOT, neither by heaven, neither by the earth, neither by any other oath: but let your yea be yea and your nay, nay; lest ye fall [as ALL of them did] into condemnation" (James 5:12). James was there that night. James was one who thought he could "perform his oath unto the Lord." But James found out that without God in him, he had no such power, and I am sure this event embarrassed James all the days of his life, and that is the reason he writes to us, "But above all things, my brethren, SWEAR NOT..."
Failing to keep an oath sworn before God breaks the 3rd commandment as well, and takes God's Name in vain. Well then, what is one way we can keep from doing this? "swear not at all." Why? "...because you can't make one hair white or black" (Matt. 5:36). Jesus said not to swear by anything, "neither by heaven, earth, Jerusalem, your head..." (Verses 34-36). Neither should we swear: "on a stack of Bibles," "on your life," "on your children's lives," or "your grandmother's grave."
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mercy, peace and love
Kat