Concerning the Ten Commandments, which are the Heads of the Law (104-106)

not indeed that any of the heavenly bodies do really wander (πεππλάνηται), inasmuch as they all enjoy a divine, and happy, and blessed nature, to all of which characteristics a freedom from wandering is most closely akin: at all events, they always preserve a kind of identity in a constantly similar motion, and pass a long eternity without ever admitting any change or variation whatever. But because they revolve in a manner contrary to the indivisible and outermost sphere, they have been named planets (πλάνητες), though without any strict propriety, by men speaking at random, who have by such language attributed their own propensity to wander to the heavenly bodies, which, in fact, never quit that position in the divine lamp in which they have been originally placed.

For all these reasons, and more besides, the number seven is honoured. But there is no one cause on account of which it has received its precedence so completely, as because it is by its means that the Creator and Father of the universe is most especially made manifest; for the mind beholds God in this as in a mirror, acting, and creating the world, and managing the whole universe.

And after this commandment relating to the seventh day he gives the fifth, which concerns the honour to be paid to parents, giving it a position on the confines of the two tables of five commandments each; for being the concluding one of the first table, in which the most sacred duties to the Deity are enjoined, it has also some connection with the second table which comprehends the obligations towards our fellow creatures;