Numbers 10:9-10

⁹When you go to war in your land against the adversary who oppresses you, then you shall sound an alarm with the shofars. Then you will be remembered before the LORD your God, and you will be saved from your enemies.

¹⁰“Also in the day of your gladness, and in your set feasts, and in the beginnings of your months, you shall blow the shofars 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.”