Matthew 5:34-37

But I say to you, do not make an oath at all, either by heaven, for it is the throne of God; or by the earth, for it is the footstool of His feet; or by Jerusalem, for it is THE CITY OF THE GREAT KING. [Ps 48:2; Is 66:1] Nor shall you make an oath by your head, for you are not able to make a single hair white or black. But let your statement be, ‘Yes, yes’ or ‘No, no’ [a firm yes or no]; anything more than that comes from the evil one. [Lev 19:12; Num 30:2; Deut 23:21]