Numbers 10:7-9 Holman Christian Standard Bible (HCSB)
7 When calling the assembly together, you are to sound long blasts, not short ones. 8 The sons of Aaron, the priests, are to sound the trumpets. Your use of these is a permanent statute throughout your generations.
9 “When you enter into battle in your land against an adversary who is attacking you, sound short blasts on the trumpets, and you will be remembered before the Lord your God and be delivered from your enemies.