Vayikra 12:4

וּשְׁלֹשִׁ֥ים יוֹם֙ וּשְׁלֹ֣שֶׁת יָמִ֔ים תֵּשֵׁ֖ב בִּדְמֵ֣י טׇהֳרָ֑הֿ בְּכׇל־קֹ֣דֶשׁ לֹֽא־תִגָּ֗ע וְאֶל־הַמִּקְדָּשׁ֙ לֹ֣א תָבֹ֔א עַד־מְלֹ֖את יְמֵ֥י טׇהֳרָֽהּ

“…She shall continue in the blood of her purifying…”

Rashi explains: The word teshev (she shall sit/dwell) means nothing other than “delaying” or “lingering,” as in the verse “And you dwelt (tishvu) in Kadesh [many days]” (Devarim 1:46), and “And he dwelt (vayeshev) by the plains of Mamre” (Bereishis 13:18).

I have always wondered why Rashi prioritized bringing these proofs to explain a word that seems clear. But now, with the help of G-d, it appears to me that Rashi, of blessed memory, intended to hint to us the true essence of “delaying” in pure blood. Just as the delay in Kadesh was for the purpose of clarifying the holy sparks that were captive there in the hands of the “shells” and the “Other Side”—as the Ohr HaChaim HaKadosh writes (Bamidbar 33:1)—so too regarding “and he dwelt in the plains of Mamre,” it was a delay meant to clarify the holy sparks that were near Mamre.

And so it is with a woman after childbirth: the “source” of red blood (representing Din or Judgment) has been opened, and it must be rectified so that the blood is uprooted and turned into milk (representing Rachamim or Mercy). For this, one must “sit,” linger, and contemplate how and by what means to sweeten these judgments. Therefore, [Rashi] prioritized the verse “And you dwelt in Kadesh,” because from there we learn the true essence of what “delaying” means.