Charles H. Spurgeon on Psalms 18:2

"The Lord is my high tower." If a man do run to a tower, yet if that be a weak and an insufficient tower, without men and munition, and a ruinous shaken tower; or if a man do make choice of a tower, a strong sufficient tower, yet if in his danger he betakes not himself to that tower, but he sit still; or if he sit not still, yet he but only go and walk on easily towards it, he may well be met withal, and a danger may arrest him, surprise him, and cut him off before he get the tower over his head. But the man that will be safe, as he must choose a strong tower, so he must go to, nay, run into that tower. Running will not secure a man unless the tower be strong. . . . David was got unto his tower, and in that tower there was thundering ordnance, and David put fire to them by prayer, verse 6, "In my distress I called upon the Lord, and cried unto my God: he heard my voice out of his temple, and my cry came before him, even unto his ears." Here David prays and gives fire to the cannon, and what followed? See verses 7, 8, 13, 14. "Then the earth shook and trembled," etc. "There went up a smoke out of his nostrils," etc. "The Lord also thundered in the heavens, and the Highest gave his voice; hail stones and coals of fire. Yea, he sent out his arrows, and scattered them; and he shot out lightnings, and discomfited them." There were no guns nor ordnance invented and in use in David's time, and yet David's prayers being in this tower, did him as good service against his enemies as all the ordnance and cannons in the world have done. David had thundering ordnance, and with them discomfited his enemies long before powder and guns were invented. It is a memorable and well known story of that Christian legion that was in Marcus Aurelius's army: the enemy being in great straits, those Christian soldiers did by their prayers not only procure rain, by which his languishing army was refreshed, but also obtained hail mixed with thunderbolts against his enemies, upon which he honoured them with the name Legio fulminatrix, the Thundering Legion. They used David's cannon against the enemy, and discharged that thundering ordnance by their prayers, and that to the confusion of their enemies. —Jeremiah Dyke's "Righteous Man's Tower," 1639.