Numbers 10:7-9 World English Bible (WEB)
7 But when the assembly is to be gathered together, you shall blow, but you shall not sound an alarm.
8 “The sons of Aaron, the priests, shall blow the trumpets. This shall be to you for a statute forever throughout your generations. 9 When you go to war in your land against the adversary who oppresses you, then you shall sound an alarm with the trumpets. Then you will be remembered before Yahweh your God, and you will be saved from your enemies.