Charles Ellicott Commentary Numbers 10:8

"And the sons of Aaron, the priests, shall blow the trumpets; and they shall be to you for a statute for ever throughout your generations." — Numbers 10:8 (ASV)

And the sons of Aaron, the priests, shall blow with the trumpets. —As Aaron had only two sons at this time, only two trumpets were needed. In most of the places in which the word hazozerah (trumpet) occurs (as, e.g.,Numbers 31:6; 1 Chronicles 15:24), this instrument appears to have been used by the priests. There are cases, however, in the later history (as 2 Kings 11:14; 1 Chronicles 16:42), in which the trumpets appear to have been used by the Levites, and perhaps by those who were neither priests nor Levites.

The number of these trumpets was increased in the time of David and Solomon. We read in 1 Chronicles 15:24 of seven priests blowing with them before the ark of God, and in 2 Chronicles 5:12 of one hundred and twenty priests blowing with them. Josephus says that Solomon made 200,000 trumpets, according to the command of Moses (Antiq., Book 8, chap. 3).