Numbers 10:8-10

⁸The sons of Aaron, the priests, shall blow the trumpets; and they shall be to you for a statute forever throughout your generations. ⁹When you go to war in your land against the adversary who oppresses you, then you shall sound an alarm with the trumpets; and you shall be remembered before Yahweh your God, and you shall be saved from your enemies. ¹⁰Also in the day of your gladness, and in your set feasts, and in the beginnings of your months, you shall blow the trumpets over your burnt offerings, and over the sacrifices of your peace-offerings; and they shall be to you for a memorial before your God: I am Yahweh your God.