Matthew 5:33-37 - The Sermon On The Mount: Taking Oaths
33 "Again, you have heard that it was said to the men of old, 'You must not swear falsely, but you must perform your oaths as a religious duty.' 34 But I tell you not to swear at all, either by heaven, for it is God's throne, 35 or by the earth, for it is His footstool, or by Jerusalem, for it is the city of the Great King. 36 Never swear by your own head, for you cannot make a single hair white or black. 37 But your way of speaking must be a simple 'Yes' or 'No.' Anything beyond this comes from the evil one.