Hastings' Dictionary of the Bible (1898)
NUM'BER. The following numbers were understood by the Hebrews to have a symbolical or representative significance: Three was deemed to have a peculiar mystic meaning. It is the number of the Deity (the Trinity), of the thrice repeated "Holy," Isa 6:3; of the threefold priestly blessing. Num 6:23-26; Daniel's three hours of prayer. Dan 6:10, etc. Four symbolizes the world or humanity. There are four winds, Eze 37:9, four beasts, Rev 4:6, and four living creatures with four faces, four wings, and four sides.
Eze 1:5-10, etc. Five, the half of ten, as in Ex 22:1; Lev 22:14; Matt 25:2, etc. The Decalogue is divided into two tables, each containing five commandments. Seven, the union of three and four, is the number of the covenants between God and man. It implies perfection.
The number occurs very frequently in connection with both holy things and things unholy; for example, the seven priests that carried seven trumpets seven times in front of the ark and around the walls of Jericho, Josh 6:4, the seven days in the week, the seven churches, Rev 1:4, the seven years of plenty in Egypt, Gen 41:26, the seven angels with seven golden vials. Rev 15:1; but also the seven heads and seven crowns of the dragon. Rev 12:3. Ten, the number of fingers (two hands), symbolizes harmony and completeness. It is the number of the fundamental commandments.
Twelve, the multiple of three and four, is also a covenant number, like seven. Hence we have the twelve tribes, the twelve stones in the high priest's breastplate, Ex 28:21, twelve apostles, twelve gates in the New Jerusalem, etc. Forty, four multiplied by ten; as the forty days of our Lord's temptation, Matt 4, the forty years in the wilderness, etc. Seventy, seven multiplied by ten; as the seventy elders of Israel, Num 11:16, the seventy disciples of our Lord. Luke 10:1.
It is very difficult, if indeed at all possible, to get the exact and definite meaning of these numbers, and we must not carry the search too far. But that they had a special meaning for the Hebrews there can be little doubt. (Compare the extended and ingenious treatment of Lange, Com. on Revelation, pp.