SEPHER YETZIRAH OR THE BOOK OF CREATION
Ten are the numbers, as are the Sephiroth, and twenty-two the letters, these are the Foundation of all things. Of these letters, three are mothers, seven are double, and twelve are simple.
Ten are the numbers of the ineffable Sephiroth, ten and not nine, ten and not eleven. Learn this wisdom, and be wise in the understanding of it, investigate these numbers, and draw knowledge from them, fix the design in its purity, and pass from it to its Creator seated on his throne.
The three mother letters A, M, SH are the foundations of the whole; and resemble a Balance, the good in one scale, the evil in the other, and the oscillating tongue of the Balance between them.