Jesus teaching on this topic is from Matthew 5:33-37. He says,

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.’  34 But I say to you, do not swear at all: neither by heaven, for it is God’s throne;  35 nor by the earth, for it is His footstool; nor by Jerusalem, for it is the city of the great King.  36 Nor shall you swear by your head, because you cannot make one hair white or black.  37 But let your ‘Yes’ be ‘Yes,’ and your ‘No,’ ‘No.’ For whatever is more than these is from the evil one.

As D. Martyn Lloyd-Jones points out in his book, Studies In The Sermon On The Mount, the teaching of the Pharisees on the subject of oaths, from verse 33, “…are not to be found anywhere in the Old Testament, which again is a proof that He was not dealing with the Mosaic law as such but with the Parasitical perversion of it.”

No doubt, according to Lloyd-Jones, they took their perverted teaching from the following Scripture passages:

Exodus 20:7: You shall not take the name of the Lord your God in vain…

Deuteronomy 6:13: You shall fear the Lord your God and serve Him, and shall take oaths in His name.

Leviticus19:12: And you shall not swear by My name falsely, nor shall you profane the name of your God: I am the Lord.

We will look at the teaching of oaths from the Mosaic teaching, the Parasitical teaching and from Jesus’ teaching.

The Mosaic teaching on Oaths

The Mosaic teaching according to the above Scriptures regarding oaths was…

• To keep people from lying.
• To restrict oath taking to the most serious and important matters. They were to be aware that God is always watching and listening.

The Pharisees and scribes teaching

•  Their attitude was legalistic. For example, adultery was seen as only a physical sin, not of the spirit. What mattered was only what could be seen, it didn’t matter about the heart sins.
• What mattered was what appears to be worldly, like going to movies, dances, bars, etc. But they neglect sins of pride, and lust.

Jesus’ Teaching on oaths

• We should never use the name of God or Christ when cursing.
• We should not swear flippantly by any creature, or by heaven, or earth, by Jerusalem, or by our head. A serious oath should only be to God (Deut. 6:13).
• We should not take oaths in ordinary conversation, but only in serious matters.

Conclusion

An oath is a promise made that we say is true. The problem today is that we constantly break those oaths. We lie. We see oath breaking too often in the political realm between countries, and also in our own country between leaders. We say we will do something and then do the opposite. We don’t keep our word. We are not honest. The breaking of oaths also happens between husband and wife, and parents and children.

Oath breaking is a serious offence. It happens openly and also secretly. It happens with all our little white lies, and also with our exaggerations—because it gives others a false impression of us. So, in all we do and say, we must always realize that we are in the presence of God and He hears us.