Numbers 10:6-8

King James Version

⁶ When ye blow an alarm the second time, then the camps that lie on the south side shall take their journey: they shall blow an alarm for their journeys.

⁷ But when the congregation is to be gathered together, ye shall blow, but ye shall not sound an alarm.

⁸ And the sons of Aaron, the priests, shall blow with the trumpets; and they shall be to you for an ordinance for ever throughout your generations.