Numbers 10:3-8

³If both trumpets are blown, it means that everyone must gather together at the entrance of the Sacred Tent.

⁴If only one trumpet is blown, it means that only the twelve leaders of the tribes must gather together.

⁵If the trumpets are blown loudly, the tribes that are to the east of the Sacred Tent should start to travel.

⁶When the trumpets are blown loudly the second time, the tribes that are to the south should start to travel. The loud blasts on the trumpet will signal that they should start to travel.

⁷When you want only to gather the people together, blow the trumpets, but do not blow them as loudly.

⁸The priests who are descended from Aaron are the ones who should blow the trumpets. That is a regulation that will never be changed.