Charles H. Spurgeon on Psalms 27:3

Though an host should encamp against me, my heart shall not fear. Before the actual conflict, while as yet the battle is untried, the warrior's heart, being held in suspense, is very liable to become fluttered. The encamping host often inspires greater dread than the same host in actual affray. Young tells us of some —"Who feel a thousand deaths in fearing one." Doubtless the shadow of anticipated trouble is, to timorous minds, a more prolific source of sorrow than the trouble itself, but faith puts a strengthening plaister to the back of courage, and throws out of the window the dregs of the cup of trembling. Though war should rise against me, in this will I be confident. When it actually comes to push of pike, faith's shield will ward off the blow; and if the first brush should be but the beginning of a war, yet faith's banners will wave in spite of the foe. Though battle should succeed battle, and one campaign should be followed by another, the believer will not be dismayed at the length of the conflict. Reader, this third verse is the comfortable and logical inference from the second, confidence is the child of experience. Have you been delivered out of great perils? then set up your ensign, wait at your watch fire, and let the enemy do his worst.