A teaching on Sukkot by Kalonymus Kalman Halevi Epstein, from Maor VeShamesh, Ramzei Shavuot
The three supernal wisdoms [called by the names of God] Ehyeh, YHVH, Ehyeh together make the gematria of chaim, “life” (1). It was because of the unity of these names at the time of the giving of the Torah that there was true coupling and unification (2), face to face (3), and so the supernal wisdoms overflowed and released their bounty onto the world… Chaim also has the gematria of lulav, which also hints at unity, as our sages said, “One who sees a lulav in a dream is of one heart with his Father in heaven” (4). [This is why the lulav and etrog must be held together,] for God forbid there should be some separation — rather, one heart, as one man, and because of this God gave the Torah to His people, in the third month, the sign of the Twins (5), and if you know the signs then you will see that the Twins are face to face, which hints at unity and love, which was the prerequisite for receiving the Torah.
1) Gematria is a system of counting the numerical value of a word (since each letter is also a number) and comparing it to other values to find hidden meanings, as we will see. 2) Between earth and heaven, between the sefirot, and between God and Israel. 3) The sefirot are often called “faces,” and when there is unity between them they are said to be “face to face” rather than “back to back”; this also evokes the Torah’s statement that Moses spoke with God “face to face” (Ex. 33:11), and the saying of the sages that the cherubim over the Ark of the Covenant faced each other when the Jews did God’s will and faced away when they didn’t (Bava Batra 99a on Exodus 29:20 and 2 Chronicles 3:13). 4) Yerushalmi, Nedarim 5) aka Gemini; a rare reference to astrology in Hasidic writing, though there is actually an extensive connection between Jewish astrology and the kabbalah.
On Shabbat Chol Hamoed Sukkot we read of the giving of the Ten Commandments on Mt. Sinai, seemingly a strange choice for Sukkot, but the Maor VeShamesh explains what’s common to both: unity. Unity between us, symbolized by the joining together of the Four Species (Vayikra Rabbah 30:12), evokes unity between us and God.