Parashas Bo · Passuk 12:1
Chabad.org — English translation + Rashi
Torah Temimah points to Mechilta (verified).
Sefaria — Exodus 12:1
Sefaria — Mechilta
English: “Saying (leimor)” — what does leimor mean? Rabbi Yishmael said: Go out and say to them at once, as it is said, “And he went out and spoke to the children of Yisrael that which he was commanded.”
In context: See the cited source for the full section.
Derash on the verse (Mekhilta) — not a formal named middah of the 13.
Moshe was to convey Hashem’s words to Yisrael immediately upon receiving them.