Rashi on Exodus 12:42/רש"י על שמות י״ב:מ״ב

1ליל שמרים IT WAS NIGHT OF WATCHING [UNTO THE LORD] — a night which the Holy One, blessed be He, was watching for and looking forward to, that He might fulfill His promise להוציאם מארץ מצרים TO BRING THEM OUT FROM THE LAND OF EGYPT.

2הוא הלילה הזה לה IT IS THIS NIGHT OF THE LORD — it is the night of which He said to Abraham, “On this night will I redeem your children” (Mekhilta; cf. Rashi on Genesis 39:11).

3שמרים לכל בני ישראל לדרתם [IT IS A NIGHT] OF PROTECTION FOR ALL THE CHILDREN OF ISRAEL THROUGHOUT THEIR GENERATIONS — this night is protected, and comes as such from ages past, against all destructive forces, as it is said, (v. 33) “And He will not permit the destroyer [to enter your houses]” (Pesachim 109b; Rosh Hashanah 11b).