Symbols used to designate quantity. The Hebrews used the decimal system, but did not develop their own symbols until the postexilic period (539 BCE on). In all preexilic inscriptions, numbers are either represented by Egyptian symbols or are written out. Some numbers in biblical usage had symbolic meaning. Seven probably represented completeness and perfection, as seen in the seven days of creation and the corresponding seven-day week, climaxing with the Sabbath (Gen 1:1-2:4). See, e.g., (Gen 41:1-36; Gen 29:15-30; Ps 12:6). Multiples of seven were also important (Exod 24:1; Exod 24:9; Lev 25:8-9; Jer 25:12; Jer 29:10; Dan 9:2). A similar use of the number seven (and multiples of seven) can be seen in the NT (Matt 18:21-22; Luke 10:1-17; Acts 6:1-6; Rev 2-3). The number three also indicated completeness (Dan 6:10; Ps 55:17; Matt 12:40). Four could be significant, since there were four cardinal directions, four corners of the earth (Isa 11:12), and the four winds (Jer 49:36). Four rivers flowed out of Eden to water the world (Gen 2:10-14). Surrounding God were four living creatures (Ezek 1:10; Rev 4:6-7). Forty, a frequently occurring multiple of four, represented a large number or a long period of time (Gen 7:12; Mark 1:12).