Tet is the ninth letter and has the value nine. Sefer Yetzirah places it among the letters of the tongue, with Dalet, Lamed, Nun and Tav. In Torah scrolls, it is one of the seven Sha'atnez Getz letters that carry three small crowns. The Talmud observes that it does not appear even once in the Torah before the word tov, "good," in the fourth verse of Genesis.
In Sefer Yetzirah, Tet is one of the twelve simples. G-d "made the letter Tet reign and bound a crown to it," and through it formed Aryeh, the Lion, in the world, the month of Av in the year and the right kidney in the body. The book also lists the twelve foundations of the simples: sight, hearing, smell, speech, taste, union, action, walking, anger, laughter, thought and sleep.
In tractate Shabbat, the children's sentence goes on: "if you do so, the Holy One, blessed be He, feeds you, is gracious to you and does good to you." Tet gives metiv, to do good. The one who does good to the poor receives, letter after letter, good in return.
Tractate Bava Kamma reports the teaching of Rabbi Yehoshua ben Levi: "One who sees a Tet in a dream, it is a good sign for him." The Talmud discusses: if it is because tov begins with Tet, many verses of misfortune also begin with Tet, such as "I will sweep it with the broom of destruction," or "her gates have sunk into the ground." It concludes: Tet is a good sign "because Scripture opened with it first for good." From "in the beginning" until "G-d saw that the light was good," no Tet is written. The Alphabet of Rabbi Akiva reads Tet as tit, the clay in G-d's hand, "as clay in the hand of the potter": the whole world was drawn from it, and everything returns to it.
Nine, good first. The Talmud does not say that the letter is good by nature, since it also opens words of ruin; it looks at the first time the Torah uses it, and that first time is the light declared good. Sefer Yetzirah associates it with the month of Av; the children of Shabbat 104a, with the good G-d does to the one who gives. A first occurrence, in the Torah, sets the meaning of a letter.