Numbers 10:2-8

2Make thee two trumpets of silver; of beaten work shalt thou make them; and they shall serve for the calling together of the assembly, and for the journeying of the camps.

3And when they shall blow with them, the whole assembly shall gather to thee at the entrance of the tent of meeting.

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

5And when ye blow an alarm, the camps that lie eastward shall set forward.

6And when ye blow an alarm the second time, the camps that lie southward shall set forward; they shall blow an alarm on their setting forward.

7And when the congregation is to be gathered together, ye shall blow, but ye shall not blow an alarm:

8the sons of Aaron, the priests, shall blow with the trumpets; and they shall be to you for an everlasting statute throughout your generations.