Seven is the sacred number—seven days, seven planets, seven chakras, seven notes. It represents the inner journey, the quest for truth, the mystic withdrawn from the world to find wisdom.
Counted: the seven doubles of Sefer Yetzirah, the seven days, the seven planets of the classical sky, the seven heavens. In the letter-values 7 is zayin.
Meaning
Seven is the tradition's number of completion in time — the week, the seventh day, the seventh year, the seven weeks to Pentecost — and Sefer Yetzirah makes it the number of the seven double letters, each pronounced two ways and governing a pair of opposites. The classical planets are seven, so the same number rules the sky, the calendar and the alphabet, which is why the septenary is the most portable structure in the whole system.