Numbers 10:8
"And the sons of Aaron, the priests, shall blow with the trumpets; and they shall be to you for an ordinance for ever throughout your generations."
Cross References (ranked by relevance)
Numbers 31:6
And Moses sent them to the war, a thousand of every tribe, them and Phinehas the son of Eleazar the priest, to the war, with the holy instruments, and the trumpets to blow in his hand.
1 Chronicles 15:24
And Shebaniah, and Jehoshaphat, and Nethaneel, and Amasai, and Zechariah, and Benaiah, and Eliezer, the priests, did blow with the trumpets before the ark of God: and Obededom and Jehiah were doorkeepers for the ark.
1 Chronicles 16:6
Benaiah also and Jahaziel the priests with trumpets continually before the ark of the covenant of God.