Numbers 10:6-8

Amplified Bible

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]. ⁷ When the assembly is to be gathered, you shall blow [the trumpets in short, sharp tones], but without sounding an alarm. ⁸ The sons of Aaron, the priests, shall blow the trumpets; and the trumpets shall be for you a perpetual statute throughout your generations.