Be'er Mayim Chaim, Exodus 12:13/באר מים חיים·שמות י״ב:י״ג

3However, it is known from the meditations of the Ari, may his memory be blessed, that the main negation and banishment of the external forces is by way of the names mentioned and put on the mezuzah, Shad-dai, ve hayah, and kaf, vav, zayin, vav, [then] bet, mem, vav, kaf, samech, zayin, etc. And it is all from the enlightenment of Understanding [Binah], the aspect of the supernal Mother. As in every place that it floats, all aspects of the external forces are subdued by its light; see there at length. Accordingly hence our forefathers who were in Egypt and did not yet have the Torah or a mezuzah, but required protection at the entrance — behold our God, may He be blessed, who has counsel and salvation, had an amazing counsel and ordered [them] to take the commandment they already had in their hands, the blood of the Passover sacrifice. As it was already sweetened and included in holiness, by way of the ritual slaughter and the intention for the commandment of the Passover sacrifice. And it is well known that the numerical equivalent of blood [dam] is the equivalent of, I shall be [Ehieh], in the quadruple expansion, like this, e, eh,, etc. which is hinted to for the enlightenment of Understanding, the aspect of the Mother. So it was put on the doorpost of the entrance and on the lintel. And through this, the destructive power could no longer come to the house, as its eyes were blinded by the enlightenment of this light, such that it fled like the flight of an arrow. So it was a great distinction for it, to distinguish between the house of an Egyptian and the house of a Jew. However, on a written mezuzah, we write these three names on it that were mentioned, and they draw from the aspect of Understanding so that they are banished through it. However, with the blood of the Passover sacrifice, it was not written with [God's] name, and [even] its essence only hints to one name, the name Ehieh. Therefore, the Holy One, blessed be He, ordered to put it on the two doorposts and on the lintel, such that there be three names of the Holy One, blessed be He, on the entrance. So through this, the entrance was surrounded on all sides, to banish the destructive power from there. And that is [the meaning of] its saying, And the blood on the houses shall be a sign for you. As this is in the aspect of a sign that is like the king's seal, which is outwardly inscribed on the garments of his servants as a sign that he is a servant of this king. And through this, everyone fears him and is afraid of him, not to touch him for the bad, since his patron is imprinted upon him. And the servant of a king is a king. And when I see the blood, etc., and there shall not be upon you a plague for the destroyer, when I smite, etc. For the smiting of Egypt was through the destructive power that He, may He be blessed, sent. And the destructive power is unable to distinguish. So the blood was a sign at the entrance to strike the people at the entrance with blindness that they should not approach there. (And if you understand well about the secret of the unity of God, may He be blessed, in the secret of and His kingdom reigns over all (Psalms 103:19), you will better understand what he wrote here, and when I see the blood, according to the things mentioned.) And see that which is written on the verse, draw and take (Exodus 12:21) — from there as well, you will correctly understand its saying, and when I see, etc.. And we will return to our topic, which is that on this night, it is the time of the rectification of all judgements of holiness. And so, all aspects of the Other Side fall and are broken. And that is why the Torah commanded...