This Ma’amar is (on the surface) very vague and difficult. The idea (seems to be) is that the splitting of sea at Yetzias Mitzrayim and of Bekias HaNahar when Moshiach comes as a preparation for the revelations of the Torah (which is Chochma) that was to follow. The Ma’amar is trying to understand how Midos can be a preparation for Mochin. He explores the various levels of Midos [1) Yaakov, ] 2) Yisroel Zuta, 3) Yisroel Sabba, [4) Yisroel Dileaila] and he explains how these four are four levels of Midos; but that they are all connected and on the highest level reveal the essence of Ta’anug (which is the source of Torah). This justifies preparing for receiving the Torah with an Avoda of Middos.
