Setting and Overview
In our first set of three antitheses, we saw Jesus address issues that could either be kept hidden from others (anger and lust) or would only apply to a smaller percentage of listeners (divorce.) In the next three, we see Him address areas in which our failings will be more obvious, and which none of us can say will never apply to us. In the first of these, Jesus on the surface addresses a matter that may seem to have little application in our time and culture: the making and keeping of vows and oaths. The core issue, however, is applicable today as it was in His time: is our word completely true and reliable?

Exposition
The “you have heard it said” that marks the beginning of this section does not directly quote the Old Testament but is primarily pulled from Leviticus 19:12 (also reflecting Exodus 20:7, Deuteronomy 6:13, 23:21-13, and Numbers 30:2), which emphasize that when someone makes an oath or vow in God’s name, that it must be kept. The Old Testament also makes clear that to substitute another name for God’s in an oath was identified with idolatry (Numbers 30:2, Jeremiah 12:14.) This didn’t mean that truthfulness only mattered when an oath was made (Leviticus 19:11, Jeremiah 9:3-5), only that the word of God’s people, which was supposed to be reliable at all times, was expected to be completely reliable when an oath in God’s name was made. Over time, traditions developed of making oaths and vows in the names of other things, and the degree to which someone was bound to their word was measured by how closely the thing was related to God’s name (Matthew 23:16-22.) Instead of encouraging honesty, this system provided excuses for dishonesty, and when someone took failed to use an oath at all, many regarded their word as meaning nothing.
We can imagine, then, how surprised that Jesus’ audience would have been to hear Him say to not take oaths at all. After all, that would seem to eliminate their last avenue to verify someone’s word. Before explaining Himself, Jesus gives four examples of things to not take oaths by. Because none of these were God’s name, the understanding was that an oath by any of them was not completely binding, but Jesus shows that such excuses will not hold up. Heaven, earth, and Jerusalem are all associated with God, so to break an oath by any is still a sin. Furthermore, an oath of self-harm (swearing on one’s head) is to claim a sovereignty over one’s life that we do not have. What is the alternative? To simply let your word be reliable at all times. If we come up with any reasons that our word is more reliable at some times than others, then we are simply excusing lies and deception, which is evil.

Examination and Application
Some groups have taken Jesus’ command here to be an absolute ban on oaths, to apply even in a legal context, but that would seem to conflict with examples in Scripture of Jesus (Matthew 26:63-34) and Paul (Romans 1:9 and others) swearing oaths, not to mention being a separate issue from Jesus’ emphasis here. As those who are called to share the truth of the Gospel with a world who will often reject it (John 8:31-32, 43-46), we must earn a reputation for absolute reliability, not to mention the importance of truth in building community (Ephesians 4:15, 25, Colossians 3:8-9) and in carrying out ministry (Ephesians 6:14.) We are blessed to know that the truth of Scripture is enough (II Timothy 2:15) and we don’t have to exaggerate or finesse it, but simply share it. For that reason, we should strive to earn a reputation for fairness, accuracy, and reliability in what we say, knowing that even a small untruth can have powerful consequences (James 3:1-6.) We must especially be careful in what we say of others (James 3:7-10) and in how we correct those who are in error (II Timothy 2:25.) Finally, we should be consistent in our word, always honoring and fulfilling what we tell others we will do (Matthew 5:33) whether we think others are counting on it or not. We should be as vigilant to follow-through as if it was a promise made in God’s name.