Numbers 10:2-8

2Make thee two trumpets of silver; of beaten work shalt thou make them: and thou shalt use them for the calling of the congregation, and for the journeying of the camps.

3And when they shall blow them, all the congregation shall gather themselves unto thee at the door of the tent of meeting.

4And if they blow but one, then the princes, the heads of the thousands of Israel, shall gather themselves unto thee.

5And when ye blow an alarm, the camps that lie on the east side shall take their journey.

6And when ye blow an alarm the second time, the camps that lie on the south side shall take their journey: they shall blow an alarm for their journeys.

7But when the assembly is to be gathered together, ye shall blow, but ye shall not sound an alarm.

8And the sons of Aaron, the priests, shall blow the trumpets; and they shall be to you for a statute for ever throughout your generations.