One must separate and remove the externalities, the shells and the darkness, which are the extraneous thoughts, and to remove from it the light of holiness that was hidden within. After making this separation, then you will take pleasure, and the advantage that light has when coming from darkness makes one a throne for the other. This is as I wrote in the name of my Master, on the Midrash: “And it was evening – these are the deeds of the wicked, etc.” Thus it is written: “And it was evening, and it was morning, one day.” Meaning to say, after making the separation, [evening] becomes a throne for morning, and therefore, the two together – evening and morning – are called “one day.” Toldos Yaakov Yosef, p. 109a, 116d²⁵

footnotes: ²⁵ See also Rav Yeibi, in his name, on Psalms 50.