Three is the child of one and two—the creative synthesis that produces something new. It represents expression, growth, and the triangle of manifestation (thought, word, deed). The first stable form.
Counted: the three mothers of Sefer Yetzirah (aleph, mem, shin), the three patriarchs, the three pilgrim feasts. In the letter-values 3 is gimel.
Meaning
Three is the first number with a middle, and Sefer Yetzirah builds the alphabet on it: three mothers, seven doubles, twelve simples — 3+7+12 = 22. The tradition reads the triad as the first thing that can be balanced, and the tree's three pillars are the same idea at the scale of the sephiroth. The three mothers themselves are air, water and fire, the elements out of which the other letters are said to be sealed.