Numbers 10:7-10

7And when the congregation is to be gathered together, ye shall blow, but ye shall not blow an alarm:

8the sons of Aaron, the priests, shall blow with the trumpets; and they shall be to you for an everlasting statute throughout your generations.

9And if ye go to war in your land against the enemy that oppresseth you, then ye shall blow an alarm with the trumpets; and ye shall be remembered before Jehovah your 1God, and ye shall be saved from your enemies.

10And in the day of your gladness, and in your set feasts, and in your new moons, ye shall blow with the trumpets over your burnt-offerings and over your sacrifices of peace-offering; and they shall be to you for a memorial before your 2God: I am Jehovah your 3God.