Numbers 10
9 Ref When 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.
10 Ref Also 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.