There is a frequent occurrence of the number seven in the Isrealite Old Testament.
For instance: the Lord commands Noah to take into the ark clean beasts by sevens, and fowls also by sevens, and tells him that in seven days he will cause it to rain upon the earth. We are also told that the ark rested in the seventh month, and the seventeenth day of the month, upon the mountains of Ararat. After sending the dove out of the ark the first time, Noah waited seven days before sending it out again. After sending the dove out the second time, "he stayed yet another seven days" ere he again sent forth the dove.
This coincidence arises from the mystic power attached to the number seven, derived from its frequent occurrence in astrology. We find that in all religions of antiquity the number seven—which applied to the sun, moon and the five planets known to the ancients—is a sacred number, represented in all kinds and sorts of forms; for instance: The candlestick with seven branches in the temple of Jerusalem. The seven inclosures of the temple.
The seven doors of the cave of Mithras. The seven stories of the tower of Babylon. The seven gates of Thebes. The flute of seven pipes generally put into the hand of the god Pan. The lyre of seven strings touched by Apollo. The book of "Fate," composed of seven books. The seven prophetic rings of the Brahmans. The seven stones— consecrated to the seven planets—in Laconia. The division into seven castes adopted by the Egyptians and Indians. The seven idols of the Bonzes. The seven altars of the monument of Mithras. The seven great spirits invoked by the Persians. The seven archangels of the Chaldeans.
The seven archangels of the Jews. The seven days in the week. The seven sacraments of the Christians. The seven wicked spirits of the Babylonians. The sprinkling of blood seven times upon the altars of the Egyptians. The seven mortal sins of the Egyptians. The hymn of seven vowels chanted by the Egyptian priests. The seven branches of the Assyrian "Tree of Life." Agni, the Hindoo god, is represented with seven arms. Sura's horse was represented with seven heads.
Seven churches are spoken of in the Apocalypse. Balaam builded seven altars, and offered seven bullocks and seven rams on each altar. Pharaoh saw seven kine, &c., in his dream. The "Priest of Midian" had seven daughters. Jacob served seven years. Before Jericho seven priests bare seven horns. Samson was bound with seven green withes, and his marriage feast lasted seven days, &c., &c.
Enough has been shown to verify the statement that, "in all religions of antiquity, the number SEVEN is a sacred number."