God ordered that priests should announce His movement of the people by blowing two silver trumpets because the Israelites would not watch the cloud continuously. The blasts from the trumpets would reach the farthest tents in the camp (cf. 1 Thess. 4:16-17).
"Whereas the cloud in Num. 9:15-23 represents the divine initiative in leadership the trumpets constitute the response of the human leadership as it summons the congregation to gather at the tent, and signals the moment of advance for each tribal group."80
The size and shape of these trumpets were probably similar to those that appear on a panel on the Arch of Titus that still stands in Rome. They were long and straight. The Israelites may have fashioned them after Egyptian models, pictures of which appear on several old Egyptian monuments.
The priests also used these trumpets in times of war in Canaan. They used them to call the people to arms and to remind them to seek God's help so He would deliver them (v. 9).
They also announced the feasts of Israel and the first day of each new month to remind the people to remember their God (v. 10). In this chapter we have the first reference to the new moon celebration (v. 10). The appearance of the new moon signaled the beginning of a new month. The Jews viewed the first day of each new month as consecrated to God in a way similar to the Sabbath (cf. Isa. 1:13). They marked this fresh beginning with special sacrifices (28:11-15) over which the priests blew the silver trumpets (v. 10; Ps. 81:3). On the new moon of the seventh month, the Feast of Trumpets, the people did no work (Lev. 23:25-25; Num. 29:1-6; 2 Kings 4:23).
In Israel's later history the priests blew these trumpets on other festal occasions as well (Ezra 3:10; Neh. 12:35, 41; 1 Chron. 15:24; 16:6; 2 Chron. 5:12; 7:6; 29:27).
"The impression that this narrative intends to give is that of an orderly and obedient departure from Sinai. The picture is a far cry from the scene which Moses saw when he first returned from the mountain and found the nation celebrating before the golden calf: the people were running wild and Aaron had let them get out of control and so become a laughingstock to their enemies' (Ex 32:25). In other words, the author is trying to make a point with this narrative. He shows that after the incident of the golden calf the Mosaic Law was able to bring order and obedience to the nation. The Law, necessitated by the disobedience of the people, was having its effect on them."81
