Numbers 10:2
Make thee two trumpets of silver; of a whole piece shalt thou make them: that thou mayest use them for the calling of the assembly, and for the journeying of the camps. Make thee two trumpets of silver; of a whole piece shalt thou make them: that thou mayest use them for the calling of the assembly, and for the journeying of the camps.
God appointed two trumpets of silver to give the signals for calling the assembly together and for directing the journeying and movements of the camps. The trumpets were carried by the sons of Aaron, who marched just behind Moses and Aaron in front of the ark, received directions from Moses, and announced them to the people through the trumpets, while each company officer gave definite directions so that none who gave attention was left ignorant of what to do. The trumpets gave clear, distinct, and certain special sounds for the different instructions, with a special signal first to call attention and then distinct orders to be obeyed attentively, so there was no confusion of sound.
The people knew and understood the signals and were expected to give attention and obey them, so their journeys could proceed in perfect order rather than confusion of movement. At the trumpet signal for breaking camp and marching, the entire camp set forward with the tabernacle borne in the midst and each tribe in its appointed position under its own standard, all watching to see in what direction the cloud would lead. Because the instructions were made known, ignorance was no excuse, and those who failed to learn or obey were responsible for their ignorance and disobedience, with refusing to learn or understand God's requirements being as blameworthy as knowingly disobeying them.
The arrangement proves that God is a God of order who is the same in the present as in the days of Moses and designs the church now to learn order and organization from Israel.