THE Mosaic Law allowed people to take certain oaths by saying something like, “I swear to you by God,” or “I swear it by the name of Jehovah.” However, in Jesus’ day, oaths had become so common that the Jews would swear to almost anything they said. They did this to make what they said more believable, but Jesus condemned this useless practice twice. He taught: “Just let your word ‘Yes’ mean yes, your ‘No,’ no.”​—Matthew 5:33-37; 23:16-22.

According to the Theological Dictionary of the New Testament, the Talmud helps us to see how common it was for the Jews to make oaths, or swear that their words were true. This is because the Talmud explains in great detail which oaths had to be kept and which oaths could be broken.

Jesus was not the only one to condemn this wrong practice. For example, Jewish historian Flavius Josephus wrote about a Jewish sect that avoided swearing. Members of that sect believed that making oaths was worse than lying. They felt that if a person had to make an oath in order for others to believe him, then that person must be a liar. The Jewish apocryphal writing Wisdom of Sirach, or Ecclesiasticus, (23:11) similarly says: “A man given to swearing is lawless to the core.” Jesus condemned making oaths about unimportant matters. If we always tell the truth, we should not have to swear to make what we say more believable.