Rashi on Exodus 12:12/רש"י על שמות י״ב:י״ב

1ועברתי AND I WILL PASS — This is not to be taken literally, but is speaks of God as one speaks of a king who passes from place to place (Mekhilta) but in this case all were punished at a single passage and in one moment.

2כל בכור בארץ מצרים ALL THE FIRSTBORN IN THE LAND OF EGYPT — also the first-born of other nations who happened then to be in Egypt. And whence may we deduce that the first-born of the Egyptians who happened to be in other countries also died? From what Scripture states: (Psalms 136:10) “To Him that smote the Egyptians in their first-born” (an unqualified statement) (Mekhilta).

3מאדם עד בהמה FROM MAN TO BEAST — He who first began the wrongdoing, from him began the punishment (Mekhilta).

4ובכל אלהי מצרים AND AGAINST ALL THE GODS OF EGYPT [WILL I EXECUTE JUDGEMENTS] — An idol of wood rotted, and one of metal melted and was poured out on the ground (cf. Mekhilta)).

5אעשה שפטים אני ה I WILL EXECUTE JUDGEMENTS, I, THE LORD — I, Myself, and not by means of a messenger (Pesikta Zotarta).