Meaning
1. Law Regarding Oaths:
The oath is the invoking of a curse upon one's self if one has not spoken the truth (Mt 26:74), or if one fails to keep a promise (1Sa 19:6, 1Sa 20:17, 2Sa 15:21, 2Sa 19:23). It played a very important part, not only in lawsuits (Exo 22:11, Lev 6:3, Lev 6:5) and state affairs (Ant., XV, x, 4), but also in the dealings of everyday life (Gen 24:37, Gen 50:5, Jdg 21:5, 1Ki 18:10, Ezr 10:5). The Mosaic laws concerning oaths were not meant to limit the widespread custom of making oaths, so much as to impress upon the people the sacredness of an oath, forbidding on the one hand swearing falsely (Exo 20:7, Lev 19:12, Zec 8:17, etc.), and on the other swearing by false gods, which latter was considered to be a very dark sin (Jer 12:16, Amo 8:14). In the Law only two kinds of false swearing are mentioned: false swearing of a witness, and false asseveration upon oath regarding a thing found or received (Lev 5:1, Lev 6:2 ff; compare Pr 29:24). Both required a sin offering (Le 5:1). The Talmud gives additional rules, and lays down certain punishments for false swearing; in the case of a thing found it states what the false swearer must pay (Makkoth 2 3; Shebhu`oth 8 3). The Jewish interpretation of the 3rd commandment is that it is not concerned with oaths, but rather forbids the use of the name of Yahweh in ordinary cases (so Dalman).
2. Forms of Swearing:
Swearing in the name of the Lord (Gen 14:22, Deu 6:13, Jdg 21:7, Rth 1:17, etc.) was a sign of loyalty to Him (Deu 10:20, Isa 48:11, Jer 12:16). We know from Scripture (see above) that swearing by false gods was frequent, and we learn also from the newly discovered Elephantine papyrus that the people not only swore by Jahu (= Yahweh) or by the Lord of Heaven, but also among a certain class of other gods, e.g. by Herem-Bethel, and by Isum. In ordinary intercourse it was customary to swear by the life of the person addressed (1Sa 1:26, 1Sa 20:3, 2Ki 2:2); by the life of the king (1Sa 17:55, 1Sa 25:26, 2Sa 11:11); by one's own head (Mt 5:36); by the earth (Mt 5:35); by the heaven (Mat 5:34, Mat 23:22); by the angels (BJ, II, xvi, 4); by the temple (Mt 23:16), and by different parts of it (Mt 23:16); by Jerusalem (Mt 5:35; compare Kethubhoth 2:9). The oath "by heaven" (Mat 5:34, Mat 23:22) is counted by Jesus as the oath in which God's name is invoked. Jesus does not mean that God and heaven are identical, but He desires to rebuke those who paltered with an oath by avoiding a direct mention of a name of God. He teaches that such an oath is a real oath and must be considered as sacredly binding.
3. The Formula:
Not much is told us as to the ceremonies observed in taking an oath. In patriarchal times he who took the oath put his hand under the thigh of him to whom the oath was taken (Gen 24:2, Gen 47:29). The most usual form was to hold up the hand to heaven (Gen 14:22, Exo 6:8, Deu 32:40, Eze 20:5). The wife suspected of unfaithfulness, when brought before the priest, had to answer "Amen, Amen" to his adjuration, and this was considered to be an oath on her part (Nu 5:22). The usual formula of an oath was either: "God is witness betwixt me and thee" (Ge 31:50), or more commonly: "As Yahweh (or God) liveth" (Jdg 8:19, Rth 3:13, 2Sa 2:27, Jer 38:16); or "Yahweh be a true and faithful witness amongst us" (Jer 42:5). Usually the penalty invoked by the oath was only suggested: "Yahweh (or God) do so to me" (Rth 1:17, 2Sa 3:9, 2Sa 3:35, 1Ki 2:23, 2Ki 6:31); in some cases the punishment was expressly mentioned (Jer 29:22). Nowack suggests that in general the punishment was not expressly mentioned because of a superstitious fear that the person swearing, although speaking the truth, might draw upon himself some of the punishment by merely mentioning it.
Philo expresses the desire (ii.194) that the practice of swearing should be discontinued, and the Essenes used no oaths (BJ, II, viii, 6; Ant., XV, x, 4).
4. Oaths Permissible:
That oaths are permissible to Christians is shown by the example of our Lord (Mt 26:63 f), and of Paul (2Co 1:23, Gal 1:20) and even of God Himself (Heb 6:13-18). Consequently when Christ said, "Swear not at all" (Mt 5:34), He was laying down the principle that the Christian must not have two standards of truth, but that his ordinary speech must be as sacredly true as his oath. In the kingdom of God, where that principle holds sway, oaths become unnecessary.
Paul Levertoff