Numbers 10:8-10

8The sons of Aaron, the priests, shall blow the trumpets; and the trumpets shall be for you a perpetual statute throughout your generations.

9When you go to war in your land against the enemy that attacks you, then sound an alarm with the trumpets, so that you may be remembered before the Lord your God, and you shall be saved from your enemies.

10Also in the day of rejoicing, and in your appointed feasts, and at the beginnings of your months, you shall sound the trumpets over your burnt offerings, and over the sacrifice of your peace offerings; and they shall be as a reminder of you before your God. I am the Lord your God.”