Part 13 · Chapter 175

And the reason they are thirteen is that the brains (Mochin) too are three — Hesed, Gevura, and Daat [i.e., HBT] — and they are three Names of YHVH, and they are divided into thirteen letters with the inclusive [one], as above. Therefore the corrections of the beard were also thirteen. Now, as was said above of the thirteen white [paths] and the thirteen locks, that they are twelve, and the thirteenth whiteness includes all the twelve, and likewise the thirteenth lock includes all the twelve — so too the thirteenth correction of the beard includes all the twelve corrections. And so it is in the eighth correction. And this is what is said in Idra Rabba, page 134, side B: "The Tanna said, these corrections are called 'days of old'... and this thirteenth includes them all."