A mystic or sacred number; it is composed of four and three, which, among the Pythagoreans, were, and from time immemorial have been, accounted lucky numbers. Among the Babylonians, Egyptians, and other ancient peoples, there were seven sacred planets. The Hebrew verb to swear means literally "to come under the influence of seven things"; thus seven ewe lambs figure in the oath between Abraham and Abimelech at Beersheba ( Gen. xxi. 28), and Herodotus describes an Arabian oath in which seven stones are smeared with blood.
There are seven days in Creation, seven days in the week, seven graces, seven divisions in the Lord's Prayer, and seven ages in the life of man; climacteric years are seven and nine with their multiples by odd numbers; and the seventh son of a seventh son was held notable.
Among the Hebrews, every seventh year was sabbatical, and seven times seven years was the jubilee. The three great Jewish feasts lasted seven days, and between the first and second were seven weeks. Levitical purifications lasted seven days; Baalam would have seven altars, and sacrificed on them seven bullocks and seven rams; Naaman was commanded to dip seven times in Jordan; Elijah sent his servant seven times to look out for rain; ten times seven Israelites went to Egypt, the exile lasted the same number of years, and there were ten times seven elders. Pharaoh in his dream saw seven kine and seven ears of corn; Jacob served seven years for each of his wives; seven priests with seven trumpets marched round Jericho once every day, but seven times on the seventh day; Samson's wedding feast lasted seven days, on the seventh he told his bride the riddle, he was bound with seven withes, and seven locks of his hair were shorn; Nebuchadnezzar was a beast for seven years; etc.In the Apocalypse, we have seven churches of Asia, seven candlesticks, seven stars, seven trumpets, seven spirits before the throne of God, seven horns, seven vials, seven plagues, a seven-headed monster, and the Lamb with seven eyes.The old astrologers and alchemists recognized seven planets, each having its own "heaven"--
The bodies seven, eek, lo hem heer anoon; Sol gold is, and Luna silver we threpe, Mars yren, Mercurie quyksilver we clepe; Saturnus leed, and Jubitur is tyn; And Venus coper, by my fader kyn. Chaucer, Prol. of the Canon's Yeoman's Tale.
And from this very ancient belief sprang the theory that man was composed of seven substances, and has seven natures.