The first letter of the Hebrew Aleph-Bet and the the first letter in the first word of the Ten Commandments (lit. “words” – aseret ha-d’varim) is the Aleph (Exodus 20:1).
Commentators find deep meaning in the form and construction of the Aleph. It is made of two yuds, one pointing up (i.e. towards heaven) and the other pointing down (towards earth). The connector between these two yuds is a vav (the sixth letter of the Hebrew aleph-bet). The gematria (the number equivalent for the letters of the aleph-bet) of the three letters yud + yud + vav (10 + 10 + 6) equals 26. 26 is the number equivalent as well for the holiest Hebrew Name of God, known as the four-letter tetragrammaton (Yud-Heh-Vav-Heh — 10 + 5 + 6 + 5 = 26). Therefore, the number equivalent of the three internal letters that form the Aleph carries the same number equivalent as the holiest four-letter name of God.
The upper Yud of the aleph represents the absolute and transcendent realm of God. The lower Yud represents the corporeal and physical world of humankind. Moses’ role as chief among the prophets is represented by the Vav which connects the lower Yud of humankind and the upper Yud of God. Moses therefore connects the lower and upper worlds, the transcendence immanence of God, the spiritual and metaphysical realm as opposed to the material and the physical world.
The number equivalence of the Hebrew vav (6), represents the six directions (north, south, east, west, heaven, and earth) signifying God’s ever-presence.
Thus, in the letter Aleph is the intimation of God’s unity with creation, the joining of the implicate and the physical, the merging of the world to come and the world that is, God’s pathos and Moses’ prophetic empathy.
Sources: I am grateful to Reuven Matheison and his article “The Inner Meaning of the Hebrew Letters” from Visions of the Psalms Through the Gate of Colors, by Moshe Tzvi HaLEvi Berger, p. xix. I am grateful also for the notes of the artist, Moshe Tzvi Berger whose primary sources were The Hebrew Letters by Rabbi Yitzchak Ginsburg; Sparks of the Holy Tongue, by Rabbi Matityahu Glazerson; and Secret of the Holy Letters, by Rabbi Yehudah Ashlag (z’l)