voluntary promises which, when once made, were to be kept if the thing vowed was right. They were made under a great variety of circumstances (Gen. 28:18; Lev. 7:16; Num. 30:2; Deut. 23:18; Judg. 11:30, Judg. 11: 39; 1-Sam 1:11; Jonah 1:16; Acts 18:18;21:23).