2 Samuel 18:16

²²Then the woman went to all the people in her wisdom. They cut off the head of Sheba the son of Bichri, and threw it out to Joab. He blew the trumpet, and they were dispersed from the city, every man to his tent. Then Joab returned to Jerusalem to the king.

²⁸So Joab blew the trumpet; and all the people stood still and pursued Israel no more, and they fought no more.

²“Make two trumpets of silver. You shall make them of beaten work. You shall use them for the calling of the congregation and for the journeying of the camps. ³When they blow them, all the congregation shall gather themselves to you at the door of the Tent of Meeting. ⁴If they blow just one, then the princes, the heads of the thousands of Israel, shall gather themselves to you. ⁵When you blow an alarm, the camps that lie on the east side shall go forward. ⁶When you blow an alarm the second time, the camps that lie on the south side shall go forward. They shall blow an alarm for their journeys. ⁷But 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. ⁹When 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.

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

⁸For if the trumpet gave an uncertain sound, who would prepare himself for war?