Numbers 10:4-6

Amplified Bible

⁴ However, if a single trumpet is blown, then the leaders, heads of the tribes of Israel, shall gather themselves to you. ⁵ When you blow an alarm, the camps on the east side [of the tabernacle] shall set out. ⁶ When you blow an alarm the second time, then the camps on the south side [of the tabernacle] shall set out. They shall blow an alarm whenever they are to move out [on their journeys].