Numbers 10:2-4

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.

3When they blow them both, all the community must come to you to the entrance of the tent of meeting.

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