Ramchal already explained in Petach 54  that BaN had to await another irradiation in order to initiate its Tikkun process — “the Partzufim (that derived) from the lights of MaH and BaN combined”, as he puts it in his comments here.
And so we’re told in Petach 61 that MaH then had all the levels that were connected through BaN connected to it, and out of them were produced the “Tree of Holiness”, which is to say, the Worlds of Atzilut, Briah, Yetzirah, and Assiyah.
 See 10:1 and note 3 to that section.
(c) 2013 Rabbi Yaakov Feldman
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