Prayer for the Fifteenth of Av

Master of the Universe, Almighty, from whom no purpose can be withheld, grant me the merit on the Fifteenth of Av (Tu B'Av) to apprehend all the secrets of the Leviathan. Grant me the secret of the "hope of the scarlet thread" (Joshua 2:18), the sign of truth (Zohar, Terumah). For the Fifteenth of Av embodies the secret of the extending of the golden scepter (of Divine favor). The Fifteenth of Av always corresponds to the Fifteenth of Adar; it is the secret of Shushan Purim, which took place in the province of Elam. According to the Atbash cipher (where the first day of Pesach corresponds to Tisha B'Av), the seventh day of Pesach corresponds to the letter Ayin (ע), which represents the secret of Elam (עילם), whose breaking brings about Shushan.
Then, this scepter—which initially represents strict judgment—is transformed into lovingkindness (Chesed), as it is written, "He will be exalted to have mercy upon you" (Isaiah 30:18). Through the dances (mecholot) performed on the Fifteenth of Av, we access the secret of the forgiveness (mechilat) of sins. This is the secret of Machlah, the daughter of Tzelofchad, who merited true teshuvah (repentance). These dances take place on the Fifteenth of Av, exactly forty days before the creation of the world on the 25th of Elul. At this time, the secret of the golden scepter is drawn down, transforming strict judgment into a thread of lovingkindness.
This reflects the verse, "You shall bind this line of scarlet thread in the window" (Joshua 2:18), which represents the thread of the Infinite Light (Ohr Ein Sof) that is revealed on the Fifteenth of Av. This is also what Avraham Avinu, peace be upon him, meant when he declared, "I have raised my hand to the Most High God... that I will not take from a thread to a shoe strap" (Genesis 14:22-23). He elevated these elements into a Terumah (holy offering) and transformed them into a song—the secret of the dances of the Fifteenth of Av.
This is the secret of the verse, "I will sing to Hashem, for He is highly exalted; the horse and its rider He has thrown into the sea" (Exodus 15:1; Zohar, Balak). It is the secret of "the God of my father, and I will exalt Him" (Exodus 15:2), signifying that Zeir Anpin (the lower Divine manifestation) becomes integrated into Abba and Imma (the higher Divine intellects of Wisdom and Understanding), and the intellects within Zeir Anpin and Nukva are elevated and absorbed into Atika Kadisha (the Holy Ancient One, the highest level of Divine Will).
This aligns with the secret of the verse, "Behold, My servant shall prosper; he shall be exalted and lifted up, and shall be very high" (Isaiah 52:13). "Exalted" refers to the aspect of the Supernal Light that transcends all other lights. The phrase "from a thread to a shoe strap" refers to the thread of Supernal Radiance (Zihara Ila'ah) drawn directly from the Infinite Light (Ohr Ein Sof)—the Light of all lights, the Ancient of all ancients, the most Hidden of all hidden things.
For Abba (the Divine Father), which represents the sefirah of Chochmah (Wisdom) within the realm of Nekudot (points of light), is exalted above all other lights. All of this is revealed on the Fifteenth of Av. On this day, these levels are integrated into the Supernal Wisdom (Chochmah Ila'ah) of Adam Kadmon (the Primordial Man, the highest spiritual realm) through the Supernal Wisdom of Arich Anpin (the Long Face, representing Divine Will). Furthermore, Binah (Understanding) ascends to the Binah of Adam Kadmon, which corresponds to the "neck" of Adam Kadmon, embodying the secret of the verse, "Your neck is like the Tower of David" (Song of Songs 4:4).