"Again, you have heard that the law of Moses says, 'Do not break your vows; you must carry out the vows you have made to the Lord.'
References for Matthew 5:33
But I say, don't make any vows! If you say, 'By heaven!' it is a sacred vow because heaven is God's throne.
And if you say, 'By the earth!' it is a sacred vow because the earth is his footstool. And don't swear, 'By Jerusalem!' for Jerusalem is the city of the great King.
Don't even swear, 'By my head!' for you can't turn one hair white or black.
Just say a simple, 'Yes, I will,' or 'No, I won't.' Your word is enough. To strengthen your promise with a vow shows that something is wrong. "
References for Matthew 5:37