1 Corinthians 14:8

To the pipe and harp, adornments of peace, P. adds for further illustration (καὶ γάρ) the warlike trumpet. This ruder instrument furnishes a stronger example: varied signals can be given by its simple note, provided there is an understanding between trumpeter and hearers; “unius tubæ cantus alius ad alia vocat milites” (Bg [2054]). Without such agreement, or with a wavering, indistinct sound, the loudest blast utters nothing to purpose: “For if the trumpet also gives an uncertain voice, who will prepare for battle?” How disastrous, at the critical moment, to doubt whether the trumpet sounds Advance or Retreat!

[2054] Bengel's Gnomon Novi Testamenti.