33 “Again you have heard that it was said to those of old, ‘You shall not swear falsely, but shall perform your oaths to the Lord.’ 34 But I say to you, do not swear at all: neither by heaven, for it is God’s throne; 35 nor by the earth, for it is His footstool; nor by Jerusalem, for it is the city of the great King. 36 Nor shall you swear by your head, because you cannot make one hair white or black. 37 But let your ‘Yes’ be ‘Yes,’ and your ‘No,’ ‘No.’ For whatever is more than these is from the evil one. (Matthew 5:33-37)
Jesus dealt with people who thought their word was only binding if given with an oath under certain conditions. If not, then they felt free not to keep their word (see Matt. 23:16-22). Such people still exist. Honesty holds little value to them, so they break their word easily and repeatedly. Some think by emphasizing or exaggerating their honesty they somehow increase their integrity. So, they swear by God, by heaven and earth, and by many other things. They assure you they are telling you the truth. For Christians, a simple “yes” or “no” is enough to establish their truthfulness. Be a person of such integrity of heart that your word is your bond. Then when you speak, others will have no need to wonder whether or not what you say is actually true.