Parashas Yisro · Passuk 19:8
Chabad.org — English translation + Rashi
Torah Temimah points to Mechilta (verified).
Sefaria — Exodus 19:8
Sefaria — Mechilta
English: “And Moshe brought back” — the Torah teaches proper conduct, that a person should return an answer to the one who sent him; so Moshe said, even though He already knows, I will return an answer.
In context: See the cited source for the full section.
Derash on the verse.
Even when the Sender already knows the outcome, the messenger returns a formal answer; the verse embeds ordinary human courtesy into the narrative of revelation.