Numbers 10:9-10

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

¹⁰And on the day of your gladness, and on your appointed festivals, and on the beginnings of your months, shall ye blow with 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 the Lord your God.