Numbers 10:2-4

10:2 “Make two trumpets of silver; you are to make them from a single hammered piece. You will use them for assembling the community and for directing the traveling of the camps. 10:3 When they blow them both, all the community must come to you to the entrance of the tent of meeting.

10:4 “But if they blow with one trumpet, then the leaders, the heads of the thousands of Israel, must come to you.