1 Samuel 17:39
And David girded his sword on his armor, and he assayed to go; for he had not proved it. And David said to Saul, I cannot go with these…
God's fighters have often been tempted to don Saul's armour, and it has always hampered them. It may have shielded them from some assaults, but it has robbed them of elasticity, and half stifled them. They are stronger far without than with it. As surely as the Church yields to the falsehood that it must be clothed with worldly power and wealth in order to fight worldly power, it surrenders its freedom and capacity to attack, though it may obtain a sort of defence. And it is not only in churches which are called "established" that the temptation of fighting the world with worldly weapons has been yielded to. Wherever Christian individuals or communities rely upon anything but the power of the indwelling Christ to make their work successful, and seek to eke out the one weapon which God gives into their hand, "the sword of the Spirit, which is the word of God," with others borrowed from the armoury of the world, they trammel themselves and invite defeat The world laughs, just as Goliath no doubt chuckled to see the stripling walking. ungainly and stiff, in Saul's armour. It likes nothing better than to reduce Christians to impotence by getting them to arm themselves out of its stores, and to fight with weapons of the pattern of its own. Goliath had long practice in using sword and javelin; David had none. It is folly to fling aside the weapons that we are used to, and to take up with new ones, on the eve of a fight. Jesus taught us how His soldiers are to be attired if they are to conquer, when He said, "Tarry ye...till ye be clothed with power from on high."
(A. Maclaren, D. D)
Parallel VersesKJV: And David girded his sword upon his armour, and he assayed to go; for he had not proved it. And David said unto Saul, I cannot go with these; for I have not proved them. And David put them off him.