The thirtieth path joins Hod, Splendour, to Yesod, Foundation, descending the left side of the lower Tree from the sphere of the intellect to the foundation. It carries the letter Resh, whose name means "head", the summit of the body, the seat of the face and the countenance, and by extension the beginning, the chief or the principal thing, the same root gives rosh, head, as in Rosh Hashanah, the head of the year.
In the Sefer Yetzirah Resh is one of the seven double letters assigned to the seven planets, and it is given to the Sun, the chief of the heavenly lights, the source of day and of life, a fitting planet for the letter of the "head" and the foremost. The seven doubles map onto the seven planets that govern the days and the visible sky, and the pairing of Resh with the Sun, the ruling light, comes directly from this ancient Jewish attribution of the alphabet to the powers of creation.