וַיּוֹצִאֵנוּ ה' מִמִּצְרַיִם. “And I will smite every firstborn in the Land of Egypt” (Ex. 12:12) - I, and not a Saraph.” The Torah states, ‘I passed by (al) the houses of the children of Israel…’ (Ex. 12:13)¹³² One might presume that the verse is suggesting that God passed through the houses of the Israelites since it says “I passed by (al) the houses,” rather than, ‘I passed over (mei’al),’ that God hopped over the homes of the Egyptians and did not enter them.¹³³ If one would presume this is the case then the plague would not have been carried out by God but by a Saraph. Therefore, the Midrash comes to tell us that this was not the case. Rather it was the Holy One and not a Saraph who performed the tenth plague. It was a great merit for the Egyptians that they were not killed by the angel of death (but by God). It allowed them to presume that their death was an atonement and allowed them to be sanctified.

footnotes: ¹³² Note that the verse that he apparently is quoting is not the same as the actual language of the verse in Exodus. Here and in many places, Rabbi Foa is not exacting in his quotations - probably because he is delivering this as a teaching orally. ¹³³ In other words, by passing over the Egyptian homes the angel of death could strike them down while the Israelites passed through their homes protecting them.