וְרָאָ֥ה אֶת־הַחֶ֖רֶב בָּאָ֣ה עַל־הָאָ֑רֶץ וְתָקַ֥ע בַּשּׁוֹפָ֖ר וְהִזְהִ֥יר אֶת־הָעָֽם׃
if, when he seeth the sword come upon the land, he blow the horn, and warn the people;
Read midrashic interpretation of Ezekiel 33:3: and classical rabbinic exegesis.