In some Masonic Rites a mystical age is appropriated to each degree, and the initiate who has received the degree is said to be of such an age. Thus, the age of an Entered Apprentice is said to be three years; that of a Fellow Craft, five; and that of a Master Mason, seven. These ages are not arbitrarily selected, but have a reference to the mystical value of numbers and their relation to the different degrees.
Thus, three is the symbol of peace and concord, and has been called in the Pythagorean system the number of perfect harmony, and is appropriated to that degree, which is the initiation into an Order whose fundamental principles are harmony and brotherly love. Five is the symbol of active life, the union of the female principle two and the male principle three, and refers in this way to the active duties of man as a denizen of the world, which constitutes the symbolism of the Fellow Craft's Degree; and seven, as a venerable and perfect number, is symbolic of that perfection which is supposed to be attained in the Master's Degree. In a way similar to this, all the ages of the other degrees are symbolically and mystically explained.
The Masonic ages are—and it will thus be seen that they are all mystic numbers—3, 5, 7, 9, 15, 27, 63, 81.