Kabbalah su Genesi 1:5

Come and behold, the supernal radiance [Binah], continues to radiate. Through this radiance, it should bring gladness to all. This is the right, which was crowned with the right to make the engravings. It is written, "How great is Your goodness, which You have laid upon those who fear You and which You have wrought for they who trust in You" (Ps. 31:20). "How great is Your goodness" alludes to the primordial light that the Holy One, blessed be He, stored away. "They who fear You" alludes to the righteous who fear sin, who are aforementioned. "And there was evening and there was morning, the first day" (Gen. 1:5) "And there was evening" from the side of darkness [Nukva] "and there was morning" from the side of light [Zeir Anpin]. And since they join together as one, it is written they are the "first day."

"And it came to pass, that when Isaac was old" (Beresheet 27:1). Rabbi Shimon said, It is written, "And Elohim called the light Day, and the darkness he called Night" (Beresheet 1:5). This verse had already been explained; nevertheless come and behold, All the actions that the Holy One, blessed be He, performs, are true, and in the secret of the upper world. And all the words of the Torah are words of faith and supernal mysteries, as they should.

Thus, it is written, "And Abraham was old, advanced in age" (Beresheet 24:1), that is, in the shining lights (of benevolences). And he is old, as it is written, "that shines ever more brightly until the height of noonday" (Mishlei 4:18). Therefore, "And Elohim called the light Day." "And the darkness he called Night." This is Isaac, who is dark, and gets to receive the night within him. Therefore, when he grew older, it is written, "And it came to pass, that when Isaac was old, and his eyes were dim, so that he could not see" (Beresheet 27:1). (he had become completely dark). Assuredly he had to be (totally) dark to cleave well to his grade.