Numbers 10:6

When they blow them, all the congregation shall gather themselves to you at the door of the Tent of Meeting.

If they blow just one, then the princes, the heads of the thousands of Israel, shall gather themselves to you.

When you blow an alarm, the camps that lie on the east side shall go forward.

But when the assembly is to be gathered together, you shall blow, but you shall not sound an alarm.

“The sons of Aaron, the priests, shall blow the trumpets. This shall be to you for a statute forever throughout your generations.

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 the LORD your God, and you will be saved from your enemies.