Numbers 10:8-10

81The priestly sons of Aaron, moreover, shall blow the trumpets; and 2this shall be for you a perpetual statute throughout your generations. 9When you go to war in your land against the adversary who 3attacks you, then you shall sound an alarm with the trumpets, that you may be 4remembered before the Lord your God, and be saved from your enemies. 10Also in the day of your gladness and in your appointed 5feasts, and on the first days of your months, 6you shall blow the trumpets over your burnt offerings, and over the sacrifices of your peace offerings; and they shall be as a reminder of you before your God. I am the Lord your God.”