Kabbalah for Exodus 12:23

As we previously explained, the words "To destroy all flesh" (Gen. 6:17) refer to the Angel of Destruction. This is why it is also written: "And He will not allow the Angel of Destruction to come into your house to smite you" (Exodus 12:23). (He does not give him permission to destroy). To "destroy all flesh" is from (the Angel of Destruction, hinted to in the verse), "The End of all Flesh is come before Me," (to ask permission). The time the Holy One, blessed be He had waited for them to repent had passed. That is, Noah had reached 600 years of age, (and He could reward him. The time had also come for the punishment of the wicked. That is why He gave permission to the Angel of Destruction) "to destroy all flesh." He said: This is what we learned in the name of Rabbi Yitzchak, who told us all this.

And she [Tamar] sat on Petach Eynayim [the entrance to the eyes] (Gen. 38:14) - Just as you say "and he [Avraham] sits at the entrance [petach] of the tent" (Gen. 18:1), and it is written "And Ad-nai passed over the entrance [petach]" (Ex. 12:23), and it is written "open [pitchu] for me the gates of righteousness etc" (Ps. 118:19) [meaning] that all eyes of the world turn to that opening. [...]