He goes on to explain Zeir Anpin’s departure from Aba and Ima, saying: when Aba unites with Ima, that is, Male with Female; that pure air, which is Chassadim, was hidden in that Aba that is from the hidden spirit within the Ancient of Days. It then incorporated the spark that was emitted from the harsh luminary hidden within Ima’s belly, referring to the judgments of Chochmah of the left within Ima.
When the two united and were comprised within each other, Chochmah of Ima was included in Chassadim of Aba and vice versa, a powerful skull emerged, referring to the head of Zeir Anpin, and it spreads to its sides, each to its own side. This resembles Atika Kadisha, wherein three heads were present as one; they are the unknowable head, Keter and concealed Chochmah. Thus, everything was joined in the three heads, as I said (in section 42).