“Let what you say be simply ‘Yes’ or ‘No’; anything more than this comes from evil.” (Matthew 5:37)
It was common practice in Jesus’ days to affirm one’s words with an oath. People took an oath by heaven, by the earth, by the city of Jerusalem, or by God’s name: “As the Lord lives…”.
Swearing was no longer limited to especially important occasions, as it had been before – think of God’s promise to give the people of Israel a land of their own (Genesis 50:24, Deuteronomy 4:31), or a promise given to a dying father (Genesis 47:31). On such exceptional, weighty occasions it can be valid to take God as a witness of your promise or of your speaking the truth. In the time of Jesus, people took oaths simply to make clear that they meant what they said.
Jesus doesn’t approve of that practice. Instead, He says: “Let what you say be simply ‘Yes’ or ‘No’”. Jesus’ followers should be completely upright and reliable, so that people can take their words at face value. They don’t need to affirm their words with an oath, since they should keep their promises anyway.
Can people trust your ‘yes’ or ‘no’?