In which you greatly rejoice, though now for a little while, if need be, you are in heaviness through manifold trials: -1 Peter 1:6
It may be asked, what is the method by which trial strengthens faith? We might answer in various ways. Trial takes away many of the impediments of faith. Carnal security is the worst foe to confidence in God. If I sit down and say, “Soul, take thine ease, thou hast much goods laid up for many years;” faith’s road is barricaded, but adversity sets the barn on a blaze, and “the much goods laid up for many years,” cease to block up the path of faith. Oh, blessed axe of sorrow, which clears a pathway for me to my God by cutting down the thick trees of my earthly comforts! When I say, “My mountain standeth firm, I shall never be moved,” the visible fortification, rather than the invisible protector, engages my attention; but when the great earthquake shakes the rocks, and the mountain is swallowed up, I fly to the immovable Rock of Ages to build my confidence on high. Worldly ease is a great foe to faith; it loosens the joints of holy valour, and snaps the sinews of scared courage. The balloon never rises until the cords are cut: affliction doth this sharp service for believing souls. While the wheat sleeps comfortable in the husk it is useless to man, it must be threshed out of its resting-place before its value can be known. Trial plucks the arrow of faith from the repose of the quiver, and shoots it against the foe.
…trial is of special service to faith when it drives her to her God. ~ C.H. Spurgeon