1. A lawful oath is part of religious worship (Deut. 10:20), wherein, upon just occasion, the person swearing solemnly calleth God to witness what he asserteth, or promiseth, and to judge him according to the truth or falsehood of what he sweareth (Exod. 20:7; Lev. 19:12; 2 Cor. 1:23; 2 Chron. 6:22–23).
Not only is an oath lawful, it should be considered an act of worship before God. The essence of an oath lies in calling God as a witness of what is said—invoking Him—as the ultimate judge of the truth or falsity of what is said. As an act of worship, an oath should be taken only upon just and solemn occasions—as in a wedding, or being sworn into membership in a local church.
2. The name of God only is that by which men ought to swear, and therein it is to be used with all holy fear and reverence (Deut. 6:13). Therefore, to swear vainly, or rashly, by that glorious and dreadful Name; or, to swear at all by any other thing, is sinful, and to be abhorred (Exod. 20:7; Jer. 5:7; Matt. 5:34, 37; James 5:12). Yet, as in matters of weight and moment, an oath is warranted by the Word of God, under the new testament as well as under the old (Heb. 6:16; 2 Cor. 1:23; Isa. 65:16); so a lawful oath, being imposed by lawful authority, in such matters, ought to be taken (1 Ki. 8:31; Neh. 13:25; Ezra 10:5).
When men swear, they are to do so in the name of the living God only. Because this is the only name to be used in a lawful oath, this means that the taking of an oath should be attended with fear and reverence. There are two ways of sinning in manner in an oath. The first is to swear by the name of the great and terrible God, but to do so frivolously. The other is to swear by the name of any other thing. Such things are not only sins, but sins to be abhorred. Nevertheless, when the occasion warrants, in matters that are weighty, an oath is lawful—regardless of the fact that we are under the new covenant. The New Testament contains numerous occasions of lawful oaths. Therefore, when the occasion is fitting, an oath should be taken.
3. Whosoever taketh an oath ought duly to consider the weightiness of so solemn an act, and therein to avouch nothing but what he is fully persuaded is the truth (Exod. 20:7; Jer. 4:2): neither may any man bind himself by oath to any thing but what is good and just, and what he believeth so to be, and what he is able and resolved to perform (Gen. 24:2–3, 5–6, 8–9). Yet it is a sin to refuse an oath touching any thing that is good and just, being imposed by lawful authority (Num. 5:19, 21; Neh. 5:12; Exod. 22:7–11).
With regard to the substance of an oath, only what is known to be the truth should be affirmed. Moreover, it is a sin to bind oneself by an oath to do a sinful thing, or to do bind oneself to fulfill something he cannot fulfill. One of the great concerns at the time of the Reformation was the question of vows of celibacy which many had taken. When they came out of Rome, were they obligated to continue to try to live in a celibate fashion? The Westminster theologians considered the unmarried state to be unnatural (unless God had given a gift of celibacy). For regular people, ungifted in this way, a vow of celibacy was sinful and to be rejected. In addition to this, in the original Confession, it was maintained that it was sinful to refuse to take an oath when a lawful authority required it. This is indicated by the sentence in bold, which was deleted by the first American Assembly of 1789.
4. An oath is to be taken in the plain and common sense of the words, without equivocation, or mental reservation (Jer. 4:2; Ps. 24:4). It cannot oblige to sin; but in any thing not sinful, being taken, it binds to performance, although to a man’s own hurt (1 Sam. 25:22, 32–34; Ps. 15:4). Nor is it to be violated, although made to heretics, or infidels (Ezek. 17:16, 18–19; Josh. 9:18–19; 2 Sam. 21:1).
Oaths are to be interpreted according to a straightforward and honest handling of the words. If a man has bound himself to a sinful condition, the oath does not bind. Examples would include an oath to kill someone, or, as mentioned above, an oath of celibacy when one did not have the gift of celibacy. But if the oath does not bind to a sinful condition, but only to a difficult or grievous one, the oath remains in effect. The authority of the oath is not affected by the spiritual condition of the one to whom the promise was made.
5. A vow is of the like nature with a promissory oath, and ought to be made with the like religious care, and to be performed with the like faithfulness (Isa. 19:21; Eccl. 5:4–6; Ps. 61:8; 66:13–14).
The same goes for vows.
6. It is not to be made to any creature, but to God alone (Ps. 76:11; Jer. 44:25–26): and that it may be accepted, it is to be made voluntarily, out of faith, and conscience of duty, in way of thankfulness for mercy received, or for the obtaining of what we want, whereby we more strictly bind ourselves to necessary duties: or, to other things, so far and so long as they may fitly conduce thereunto (Deut 23:21–23; Ps. 50:14; Gen. 28:20–22; 1 Sam. 1:11; Ps. 66:13–14; 132:2–5).
A vow is not to be made to any creature, but only to God. It is a freewill offering, not made under compulsion. The motive force is faith and conscience of duty. The reasons we may pay our vows may be thankfulness for mercy, or for material blessings. When we receive such things, we set up fences for ourselves, in order that we may serve God effectively in our new station.
7. No man may vow to do any thing forbidden in the Word of God, or what would hinder any duty therein commanded, or which is not in his own power, and for the performance whereof he hath no promise of ability from God (Acts 23:12, 14; Mark 6:26; Numb. 30:5, 8, 12–13). In which respects, popish monastical vows of perpetual single life, professed poverty, and regular obedience, are so far from being degrees of higher perfection, that they are superstitious and sinful snares, in which no Christian may entangle himself (Matt. 19:11–12; 1 Cor. 7:2, 9; Eph. 4:28; 1 Pet. 4:2; 1 Cor. 7:23).
To reiterate an earlier point, no man may lawfully vow to do an unlawful thing. Nor may he vow to do something which would hinder him in his duties, or make a vow he is unable to perform, and has no reason to suppose that God will enable him to perform it. Specifically, the vows of perpetual celibacy, assumed poverty, and obedience to the standards of a monastic order, are not at all examples of super-spirituality. They are actually superstitions and horrible traps, in which no Christian should remain. A good contemporary example of this kind of vow is the common vow, which many evangelicals have taken, to abstain from any alcoholic beverage in any form. In all such things, the devil is up to his regular tricks . . . taking wonderful things away from us.