"I Swear to God!" What Does Jesus Say About This? - Matthew 5:33-37

Oaths

33 “Again, you have heard that it was said to the people long ago, ‘Do not break your oath, but fulfill to the Lord the vows you have made.’ 

Jesus uses the familiar refrain, "You have heard it said".  This time he is referring to the 2nd commandment, "Do not take the Lord's name in vain." The Pharisees in a similar way were more about the spirit of the Law, than the letter of the Law. 

The Pharisees had twisted the 2nd commandment by making vows in just about every other name other than God. For example, they would swear by the temple, by the head, by heaven, by the earth. So long as they kept from swearing by the name Yahweh, and so long as they observed the oaths publicly taken, they seemed to consider all others as allowable, and allowedly broken. This is the abuse which Christ wished to correct. (Barnes)

34 But I tell you, do not swear an oath at all: either by heaven, for it is God’s throne; 

The bottom line is that Jesus tells them not to make oaths at all.  When you give your word there is no need to bring God into it so as to add substance to your claim. 

As a kid, I am sure you remember saying when you got caught doing something wrong, or you were trying to get out of something, "I swear to God I didn't do it."  Though it seemed somewhat innocent at the time, it subtly diminished the meaning of God's name, as if invoking God's name was merely a get of trouble for free card.

35 or by the earth, for it is his footstool; or by Jerusalem, for it is the city of the Great King. 

In a similar way oaths were made to inaminate earthly objects. This was equally bad because it equated the power of the things on earth with the things of God.  The earth is God's footstool so swearing by earth is similar to swearing by heaven, because they are both his. 

36 And do not swear by your head, for you cannot make even one hair white or black. 

Neither shalt thou swear by thy head - This was a common oath. The Gentiles also used this oath. To swear by the head was the same as to swear by the life; or to say, I will forfeit my life if what I say is not true. God is the Author of the life, and to swear by that, therefore, is the same as to swear by him.

Because thou canst not make one hair white or black - You have no control or right over your own life. You cannot even change one single hair. God has all that control; and it is therefore improper and profane to pledge what is God's gift and God's property; and it is the same as swearing by God himself. (Barnes)

37 All you need to say is simply ‘Yes’ or ‘No’; anything beyond this comes from the evil one.

This final statement ties together all of the above teaching.  If you are speaking the truth, you don't have to swear by anyone or anything, especially God's name. And, in fact, invoking God's name to add to your claim is really trying to manipulate and use Him for your own ends. Hence the term, "using His name in vain." 

I love what Proverbs 10:19 says in the New King James Version, "In the multitude of words sin is not lacking, But he who restrains his lips is wise."

The next time you are tempted to say, "I swear to God", think about your words and why you are using them.  Is your own word not good enough?  If people don't trust what you are going to say, what is the real issue?  

Let's choose our words wisely and may they be used to speak the truth in love, and build up our fellow brothers and sisters in Christ.  If you are speaking the truth God will back your words up. You don't have to use His name in vain to prove yourself.