Read Matthew 5:33-37
33 “You have also heard that our ancestors were told, ‘You must not break your vows; you must carry out the vows you make to the Lord.’ 34 But I say, do not make any vows! Do not say, ‘By heaven!’ because heaven is God’s throne. 35 And do not say, ‘By the earth!’ because the earth is his footstool. And do not say, ‘By Jerusalem!’ for Jerusalem is the city of the great King. 36 Do not even say, ‘By my head!’ for you can’t turn one hair white or black.37 Just say a simple, ‘Yes, I will,’ or ‘No, I won’t.’ Anything beyond this is from the evil one. (NLT)
Good things can become bad things in time. The people of God made solemn vows and oaths. They were meant to add solemnity to their words. Much like swearing an oath in a law court is a reminder of the seriousness of the need for integrity. A word backed up by a vow was to be taken as truth.
But over time, the good thing was twisted. Clever people manipulated things so that certain oaths were meant to be taken seriously while other oaths could be disregarded. Word games were being played. My vow might sound solemn and sincere but if I used a certain form of words, or if I omitted certain words, then the vow was meaningless.
This sort of thing leads to breakdown of relationships. If we can’t believe one another, if we are misleading one another by cunning use of phrases, then no one can trust anyone. Jesus cuts through all this by urging us to keep our speech simple and sincere. If a civil authority asks us to take an oath, we can do so. But Jesus’ teaching suggests that for his people such oaths ought not be necessary. Our word should be enough.
Truthfulness and trust are ultimately matters of the heart and will, not of words and phrases.