1 Corinthians 14:8

For if the trumpet give an uncertain sound
That is not plain and manifest, so as that it cannot be known on what account it is given:

who shall prepare himself to the battle?
the allusion is to the custom of many nations, Jews and others, who, when about to engage in war, made use of musical instruments, particularly the trumpet, to gather the soldiers together, prepare them for the battle, give them notice of it, and animate them to it ^F25; the sound of the trumpet was the alarm of war; see ( Jeremiah 4:5 Jeremiah 4:19 Jeremiah 4:21 ) ( Job 39:25 ) . And particularly the allusion may be to the two silver trumpets, ordered by God to Moses for the Jews, which were to be made of a whole piece, and to be used for the calling of the assembly, and for the journeying of the camps, and to blow an alarm with when they went to war against the enemy, ( Numbers 10:1 Numbers 10:2 Numbers 10:9 ) and were a lively emblem of the Gospel, whose use is to gather souls to Christ, to direct saints in their journeying, and to prepare and animate them for battle, with their spiritual enemies; and of which use it is, when it gives a certain and even sound, as it does when clearly and rightly blown; and that is, the sound of love, grace, and mercy, to the sons of men, through a bleeding Saviour; salvation alone by a crucified Jesus, peace and pardon by his blood, justification by his righteousness, and atonement by his sacrifice; when it is blown aright, it blows a blast on all the goodliness of man, it magnifies the grace of God, exalts the person of Christ, debases the creature, shows its impurity, imperfection, and inability; and expresses the nature, use, and necessity of efficacious grace; and puts believers on doing good works for necessary uses, but not for life, righteousness, and salvation; and so its sound is equal, even, and certain: and when it is so, it is a means of gathering souls to Christ, the standard bearer and ensign of the people; and of engaging them to enlist themselves as volunteers in his service; and of animating them to fight under his banner the battles of the Lord of hosts: but if this trumpet gives an uncertain sound, as it does when grace and works are blended together in the business of salvation; and faith or works put in the room of, or joined with the righteousness of Christ in justification; when particular election and general redemption, or the salvability of all men, are put together; the covenant of grace represented as conditional, and preparations for grace, and offers of grace, and days of grace talked of, that may be past and lost; then who can prepare himself for the battle? persons must be thrown into, and left in the utmost uncertainty and confusion: when this is the case, they know not what side to take on, but halt between two opinions; they know not what that faith is they are to fight and earnestly contend for; they are not able to discern an enemy from a friend; they have no heart to fight and endure hardness, as good soldiers of Christ; nor can they promise themselves, or be assured of victory, which the certain sound of the Gospel gives them.