Nefesh HaChayim, Reb Itzele's Long Annotation

And then the order of their being drawn and the way they couple in their combinations is: the mem first—the four supernal roots. And then the lamed—drawing their actions which are the three elements Fire, Wind and Water, excluding the element of Dust. Everything is still in the form of intellection517Heb.: has-ka-la (using the letters sin and kaf, as in the word sei-khel) and what surrounds the brains alone. After that they unfold in meedote and in action, three-times-three, and that’s tzadiq as we mentioned above. This is for the first mating which is dependent only on the degree of holiness of the father and mother.