Q: What is the significance of the number 18?
A: The main thing that we can learn from 18, Chai, is the fulfillment of Torah and commandments (mitzvot), as in the verse, "V'chai bahem," "and you should live by them (mitzvot)."
Kabbalah teaches that 18 corresponds to the power of ratzon, ("will"), in the soul. This is the third and lowest head of the keter. The commandments of the Torah are the will of G-d. When a person performs a commandment, he gives G-d, as it were, nachat ruach, "pleasure," in that he performed G-d's will. Ratzon ("will") corresponds to Arich, which is also Arichut Yamim, ("long life"). This of course, corresponds to chai, 18. The long life alluded to here is in the merit of the commandments that the person performs.
There are 32 paths of wisdom, and 50 gates of understanding. In addition, there are 72 "bridges" of chesed, lovingkindness. 32 = 2 times 4 squared; 50 = 2 times 5 squared; 72 = 2 times 6 squared. This suggests the general expression 2 times n squared: 2, 8, 18, 32, 50, 72, 98, 128, 162, 200, 242, 288…
288 corresponds to the fallen sparks which we must redeem. The first three numbers, 2,8 and 18 correspond to the three "heads" ofketer, which are faith, pleasure and will. Following that are wisdom, 32, and understanding, 50 etc.
The above series of numbers combines in pairs to form multiples of 26, which is G-d's Name, Havayah: 2 plus 50 = 52; 8 plus18 = 26; 32 plus 72 = 104.
The 231 gates of Sefer Yetzirah refer to the 231 two-letter combinations of the 22 letters of the Hebrew alphabet. (This refers to combinations of different letters only.)
231 is also the triangle of 21, G-d's Name. 1 plus 2 plus 3…..plus 21 = 231. 21 is the triangle of 6. 6 is the triangle of 3. 3 is the triangle of 2. Thus, 231, is a triangle of a triangle of a triangle.
Obviously, all of the above has deep meaning. This is but a brief explanation.
