"Of David, when he changed his demeanor"
This verse explains that the phrase refers to the moon, that is separated on this day from the Other Side, and joins with the sun. It contains the 22 letters that the sun brings into the moon.
The 22 letters of the Hebrew alphabet signify 22 primeval forces of energy that combined together in countless configurations to conceive all Creation. They are the instruments of the Divine, tools to fashion supernal and mundane worlds, along with the diversity of life forms that inhabit them. Accordingly, this passage offers us nothing less than the Light of Creation. This illumination separates our souls from the Other Side, our Evil Inclination. Our prayers are strengthened, our spirit is renewed, and our existence is brightened so that darkness, never again, dominates our world and our souls.
209. Afterwards, ONE SHOULD SAY THE PRAISE, WHICH IS THE SECRET OF the moon, WHICH IS MALCHUT, that is separated from the Other Side on this day, in order to shine from the sun. It is written, "Of David, when he changed his demeanor... " (Tehilim 34:1). After it was separated from the Other Side, it joined with the sun, WHICH IS ZEIR ANPIN. This praise is in THE ORDER OF the 22 letters AT THE BEGINNINGS OF THE VERSES, that the sun brings them into the moon. This praise also CONTAINS the separation of the moon from the Other Side, and the praise of the 22 letters that the sun brings into the moon.
209. וּלְבָתַר סִיהֲרָא דְּקָא מִתְפָּרְשַׁת מִסִּטְרָא אַחֲרָא בְּיוֹמָא דָּא, בְּגִין לְאִתְנָהֲרָא מִן שִׁמְשָׁא, וְדָא אִיהוּ לְדָוִד בְּשַׁנּוֹתוֹ אֶת טַעְמוֹ וְגוֹ.' וּלְבָתַר דְּאִתְפָּרְשַׁת מִנֵּיהּ, הָא אִתְחַבְּרָת בְּשִׁמְשָׁא. וְתוּשְׁבַּחְתָּא דָּא בְּכ"ב אַתְוָון, דְּאָעִיל בָּהּ שִׁמְשָׁא בְּסִיהֲרָא. וְתוּשְׁבַּחְתָּא דָּא, פְּרִישׁוּ דְּסִיהֲרָא מִסִּטְרָא אַחֲרָא, וְתוּשְׁבַּחְתָּא דְּכ"ב אַתְוָון בִּנְהִירוּ דְּשִׁמְשָׁא.