Jamieson, Fausset and Brown on Numbers 10:8

8. the sons of Aaron the priests shall blow with the trumpets, &c.--Neither the Levites nor any in the common ranks of the people could be employed in this office of signal giving. In order to attract greater attention and more faithful observance, it was reserved to the priests alone, as the Lord's ministers; and as anciently in Persia and other Eastern countries the alarm trumpets were sounded from the tent of the sovereign, so were they blown from the tabernacle, the visible residence of Israel's King.