Tav is the twenty-second and last letter of the alphabet, and its value is four hundred. It has no final form. Its name also means a mark, as in the verse of Ezekiel quoted by Rabbi Akiva: "set a tav on the foreheads of the men."
In Sefer Yetzirah, tav is the last of the seven double letters, bet, gimel, dalet, kaf, peh, reish, tav, which are pronounced in two ways, soft and hard. Their foundations are life, peace, wisdom, wealth, grace, seed and dominion, each with its opposite. For tav the book writes: "He made the letter tav king, He bound a crown to it," and formed through it the Moon in the world, Shabbat in the year and the mouth in the soul. Shabbat, the seventh day, and the mouth, the seventh gate of the face, thus fall to the last of the doubles. In the classification of sounds, tav belongs to the letters of the tongue, dalet, tet, lamed, nun, tav.
The Talmud reports the reading of the alphabet that children once gave in the study hall, which the Sages came to relate to Rabbi Yehoshua ben Levi. "Shin: sheker, falsehood; tav: emet, truth." Why are the letters of sheker adjacent, and those of emet far apart? Because falsehood is common and truth is rare. Why does sheker stand on a single foot, and emet on bases as wide as bricks? Because truth stands, and falsehood does not stand. Emet is written alef, mem, tav: the first letter, the middle one and the last.
The Alphabet of Rabbi Akiva tells that the twenty-two letters, engraved with a pen of flame on the crown of the Holy One, blessed be He, came down before Him when He wished to create the world. Tav entered first and pleaded: through me You give the Torah to Israel, "the Torah that Moses commanded us." The answer was no: through you I will mark the foreheads of men, as Ezekiel says; a tav of ink on the foreheads of the righteous, tichyeh, you shall live, a tav of blood on the foreheads of the wicked, tamut, you shall die. The text adds that the attribute of Justice demanded the tav of blood even for the righteous, because they had not rebuked the others, and that to the objection "they would not have listened," it replied: they should have rebuked all the same. And tav went out, downcast.
The sources make tav the letter of truth and of the mark. Truth, says the Talmud, stands on a wide base and embraces the whole alphabet; for Rabbi Akiva, the mark of the tav decides life, and it also engages the responsibility of the righteous toward others.
