“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.’ But I say to you, do not swear at all: neither by heaven, for it is God’s throne; nor by the earth, for it is His footstool; nor by Jerusalem, for it is the city of the great King. Nor shall you swear by your head, because you cannot make one hair white or black. 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.
When Jesus quotes the Old Testament as prohibiting false vows and other oaths (Deuteronomy 23:23), He probably also has in view the Ten Commandments, as in Matthew 5:21, 27. In this case He alludes to the third commandment: a false oath “misuses” or takes in vain God’s name, since oaths by definition called on a deity to witness them (Exodus 20:7). Breaking an oath was dangerous, for in all societies oaths contained curses that deities would avenge if the person who swore by them broke the oath. The Bible’s point in prohibiting false oaths, however, was that one should tell the truth and keep one’s promises. The Hebrew Bible approved of some oaths and vows (as in Numbers 5:19–22; 6:2), but Jesus again summons us beyond the law’s letter to its intention. His own point is not so much that oaths are evil as that the motivation for engaging in them is; one should simply tell the truth.
Although Jesus’ position on oaths is not wholly unique, it was rare enough to be distinctive. Although some Jewish teachers warned against customary oath-taking, nearly all accepted oath-taking as valid; in daily life, it was surely common in the marketplace. Some groups of Essenes may have avoided oaths altogether, except for their initiatory oath for joining the sect. The historian, Josephus declares that one could trust an Essene’s word more than an oath, however; Philo indicates that their abstention from oaths declared their commitment to truth. Jesus and the Essenes probably intended the same: let your word carry such conviction that you need not call deities to witness.
The point of this passage is integrity. Jesus observes that since God witnesses every word we say anyway, we should be able to tell the truth without having to call God to witness by a formal oath. Jesus is addressing a popular abuse of oaths in His day. To protect the sanctity of the divine name against inadvertent oath-breaking, common Jewish practice introduced surrogate objects by which to swear. Jewish history tells that some people apparently thought it harmless to deceive if they swore oaths by something like their right hand. The further removed the oath was from the actual name of God, the less danger they faced for violating it. Jewish teachers had to arbitrate which oaths were actually binding as allusions to God’s name even though His name wasn’t specifically used. Jesus teaches that all oaths invoke God’s witness equally. Just as heaven, earth (Isaiah 66:1–2) and Jerusalem (Psalm 48:2; Matthew 4:5; 27:53) belong to God, so do the hairs on our heads; although we can dye our hair, we have no genuine control over its aging (compare Matthew 6:27). All oaths implicitly call God to witness, because everything that exists was made by him. For Jesus, no aspect of life except sin is purely secular.
Avoiding oaths is thus inadequate; the issue is telling the truth, because God witnesses every word we speak. Although some passages in the Bible seem to allow some degree of deception to preserve life, such exceptions are rare in our daily lives. When we lie to cover our own wrong motives from those we think would disdain us, we forget that one day God will expose all the secrets of our hearts anyway (Matthew 10:26). When we lightly commit ourselves to meet people at particular times and then unnecessarily delay them (as if their time were a commodity less precious than our own), we treat them unjustly and deceitfully, even if in a relatively minor way. How much more deceitful is it when we make promises in business deals or make still more lasting vows (such as the marriage covenant see Matthew 5:31–32).
Making vows (promises) to God lightly is a severe offense (compare Acts 5:1–11). Although Jesus’ first followers continued to call on God to witness the truth of some of their statements, apparently taking Jesus’ words as rhetorical overstatement (examples appear in Romans 1:9; 9:1; Galatians 1:20), they seem to have refrained from more overt oaths (2 Corinthians 1:17; James 5:12). Oaths that invite penalties on oneself for violating them (“cross my heart and hope to die”) are unnecessary for God’s people when truth is the standard and bar set by Jesus Himself.