Numbers 10 - 11

1 And the Lord spoke to Moses, saying: 2 “Make two silver trumpets for yourself; you shall make them of hammered work; you shall use them for calling the congregation and for directing the movement of the camps. 3 When they blow both of them, all the congregation shall gather before you at the door of the tabernacle of meeting. 4 But if they blow only one, then the leaders, the heads of the divisions of Israel, shall gather to you. 5 When you sound the advance, the camps that lie on the east side shall then begin their journey. 6 When you sound the advance the second time, then the camps that lie on the south side shall begin their journey; they shall sound the call for them to begin their journeys. 7 And when the assembly is to be gathered together, you shall blow, but not sound the advance. 8 The sons of Aaron, the priests, shall blow the trumpets; and these shall be to you as an ordinance forever throughout your generations ...
— NUMBERS 10 - 11