Numbers 10:8

4 But if only one is sounded, then the leaders, the heads of the clans of Israel, are to gather before you.

5 When you sound short blasts, the camps that lie on the east side are to set out.

6 When you sound the short blasts a second time, the camps that lie on the south side are to set out. The blasts are to signal them to set out.

7 To convene the assembly, you are to sound long blasts, not short ones.

8 The sons of Aaron, the priests, are to sound the trumpets. This shall be a permanent statute for you and the generations to come.

9 When you enter into battle in your land against an adversary who attacks you, sound short blasts on the trumpets, and you will be remembered before the LORD your God and saved from your enemies.

10 And on your joyous occasions, your appointed feasts, and the beginning of each month, you are to blow the trumpets over your burnt offerings and fellowship offerings to serve as a reminder for you before your God. I am the LORD your God.”

11 On the twentieth day of the second month of the second year, the cloud was lifted from above the tabernacle of the Testimony,

12 and the Israelites set out from the Wilderness of Sinai, traveling from place to place until the cloud settled in the Wilderness of Paran.

Read all of Numbers 10