Number Two - Brings in complimentary opposites of light and dark, men and women.
Number Three - Completes a dynamic triangle, energy is created and everything begins to expand.A man and a woman together for example, create a child.
In Christianity The Holy Trinity, is God the father, The Son and the Holy Spirit. Traditionally, Christians wear a crucifix to represent the sacred three.
The first time you recite your incantation you are making a statement to the universe. the second time invokes the energy of the universes' complimentary opposite. The third incantation completes the circuit and brings the spell to life.Repeating the whole process twice more results in making your incantation nine time - three to 'the power of three'
This repetition increases your concentration and focus, helping you resonate wit the threefold nature of the universe. When we do anything in threes, there is a sense of completion.
In Feng Shui, a symbol of trinity is used for good luck - three coins places together in a triangular fashion are hung over doorways as a prosperity sign.