Also see definition of "Vow" in Word Study
Study Dictionary
Vow
VOW [ISBE]
VOW - vou (nedher; euche; 'iccar, found only in Nu 30:6,8,10 and translated horismos, by the Septuagint: A vow could be positive (nedher) and included all promises to perform certain things for, or bring certain offerings to, God, in return for certain benefits which were hoped for at His hand (Gen 28:20-22, Jacob; Lev 27:2,8; Nu 30; Jdg 11:30, Jephthah; 1 Sam 1:11, Hannah; 2 Sam 15:8, Absalom; Jon 1:16, vows of heathen); or negative ('iccar), and included promises by which a person bound himself or herself to abstain from certain things (Nu 30:3). Nowhere in the Old Testament do we find the making of vows regarded as a religious duty (Dt 23:22), but the fulfilling of a vow was considered as a sacred and binding duty (Dt 23:21-23; Jdg 11:35; Eccl 5:4; compare Ps 22:25; 66:13; 76:11; 116:18). A vow was as binding as an oath (see OATH) and therefore to be kept to the letter; and it was not to be lightly made (Prov 20:25). A father could veto a daughter's vow, and a husband a wife's. If a husband did not veto a wife's vow, and then caused her to break it, the sin was his and not hers (Nu 30, passim). It seems that vows were considered binding only when actually uttered (Dt 23:23). Persons, including one's self, animals, land and other possessions, could be vowed, but all these could be redeemed with money (see JEPHTHAH), which money was to be estimated by the priest, except in the case of a clean animal. In the case of land, houses and unclean animals a fifth part of the estimated value was to be added to make up the redemption money. In the case of land the sum was greater or smaller as the coming year of Jubilee was far off or near (Lev 27, passim). Nothing which was by nature holy could be made the object of a vow, e.g. firstlings, tithes, etc. (Lev 27:26,28,30); and, on the other hand, an abomination, e.g. the hire of a prostitute, could not be made the object of a vow (Dt 23:18). In Mal 1:14 the offering of what was of less value than what had been vowed is vigorously condemned.In the New Testament Jesus refers to vows only to condemn the abuse of them (Mt 15:4-6; Mk 7:10-13; compare Talmud, Nedharim, and see CORBAN). In Acts 18:18 (compare Acts 21:23,24) Paul desires to show his Jewish brethren that he is willing to keep the forms of Jewish piety so long as they do not clash with his Christian conscience (compare 1 Cor 9:21). For the vow of the Nazirite, see NAZIRITE.
Paul Levertoff
Also see definition of "Vow" in Word Study