Numbers 10:6

3 When they are sounded, all the people are to come together to you at the door of the Tent of meeting.

4 If only one of them is sounded, then the chiefs, the heads of the thousands of Israel, are to come to you.

5 When a loud note is sounded, the tents placed on the east side are to go forward.

6 At the sound of a second loud note, the tents on the south side are to go forward: the loud note will be the sign to go forward.

7 But when all the people are to come together, the horn is to be sounded but not loudly.

8 The horns are to be sounded by the sons of Aaron, the priests; this is to be a law for you for ever, from generation to generation.

9 And if you go to war in your land against any who do you wrong, then let the loud note of the horn be sounded; and the Lord your God will keep you in mind and give you salvation from those who are against you.