Numbers 10:7-9

New Revised Standard Version Catholic Edition

⁷ But when the assembly is to be gathered, you shall blow, but you shall not sound an alarm. ⁸ The sons of Aaron, the priests, shall blow the trumpets; this shall be a perpetual institution for you throughout your generations. ⁹ When you go to war in your land against the adversary who oppresses you, you shall sound an alarm with the trumpets, so that you may be remembered before the Lord your God and be saved from your enemies.