The number 3 is said to represent the triple Goddess and/or God, the Lunar Phases; the mental, physical, and spiritual aspects combined.

The spell casting or works that go well with this number correspondence are: action, ambition, authority, balance (mental), beauty, beginnings, communication, connections, control, creativity, crossroads, cycles, discipline, endings, fertility, friendship, growth, harmony, healing, imagination, life, love, luck, magick (moon), manifestation, the mind, motivation, pleasure, pride, protection, psychic ability, results, success, unity

*Some of this information was taken from Llewellyn’s complete book of correspondences by Sandra Kynes*