ירמיהו מב:כא פירוש: רד״ק ורש״י

That we send. In the verse it is written Anu, but we read anaḥnu, and this matter is unique, but the word anu>/i> is not found elsewhere in Tanakh, but is common in the language of Mishnah and Talmud.

the sound of the horn which the lookouts sound to warn the people.