In the case of Ze’er Anpin, there is another factor at work: Its partition does not draw the vessels of the first three, since it is a partition of the first level,190Since the partition at the bottom of Ze'er Anpin only has the opacity of the first level, it can only create returning light of the height of Ze'er Anpin, meaning of the six extremities, as opposed to a height tall enough to enclothe the first three sefirot (as explained in the preceding sections). and therefore the upper partzuf cannot give the lower partzuf brains from the fusion through collision of the partition with the supernal light.
This is why the aforementioned third criterion is required, that Ze'er Anpin receive the brains by causing the emergence of brains in its upper partzuf, constituting the mystical meaning of “three come out of one; one exists in three,” as stated above.191See section 68.