“Go back to the Old Testament. We find Moses leading those grumbling, recalcitrant children of Israel. They come to him one day and say: ‘There is no water here; have you brought us out of Egypt in order that we may die of thirst here in the wilderness? There is no water; everything is as dry as a bone; what can we do?’ And God told Moses to strike a rock, informing him that when he did so water would come pouring out of it. Now there lies the predicament. Moses was a man, and though he was a very good man he knows that if he strikes rocks nothing will happen. He may have struck many a rock but no water had come gushing out. But here he is told that if he strikes a certain rock with his rod water will come gushing out of it. That constitutes the whole predicament of faith. That is exactly the position of all of us as we stand face to face with the command: ‘Be strong in the Lord, and in the power of his might’. ‘But who am I?’ you say. ‘I am just a weakling. What is the use of telling me to be strong?’ The answer is this. Moses in faith took his rod and he smote, he struck, the rock; and out of it came the water gushing forth. It was not Moses’ power, but it was his arm and it was his rod. Moses did not just stand by and see the water gushing out. Moses had to lift up his arm and he had to strike, to smite, that rock. But as he did so the power was given to him, and the water came gushing out of the rock. There you see the two elements in this matter. You see the activity of the man, but you see that the power is given to him by God. It was not Moses—Moses lacked the power to do such things. But Moses was given the power to do them. The two things come together. But the point I am emphasizing now is that Moses, if he had hesitated there, and had done nothing, would not have seen this marvellous miracle; but by acting he discovered that the power was given. He ‘tasted’ and he ‘saw’! That is the way in which it happens.” D. Martyn Lloyd-Jones, The Christian Soldier
No Other Boast 