וּתְקַעְתֶּ֤ם תְּרוּעָה֙ שֵׁנִ֔ית וְנָֽסְעוּ֙ הַֽמַּחֲנ֔וֹת הַחֹנִ֖ים תֵּימָ֑נָה תְּרוּעָ֥ה יִתְקְע֖וּ לְמַסְעֵיהֶֽם׃
And when ye blow an alarm the second time, the camps that lie on the south side shall set forward; they shall blow an alarm for their journeys.
Read midrashic interpretation of Numbers 10:6: and classical rabbinic exegesis.