From: Gurnall, William. The Christian in Complete Armour: A Treatise of the Saints’ War against the Devil … London: Banner of Truth Trust, 1964.
“Every creature has its proper diet: the lion does not eat grass, nor the horse, flesh. Just so, what is food to the carnal heart, is poison to the gracious; and what is tasty to the gracious, is odious to the carnal. The Spirit lusts against the flesh and the flesh against the Spirit throughout the whole course of a Christian’s life. Were there no devils, you would still have your hands full resisting the corruptions of your own heart. What Paul, in Ephesians 6:12, wants you to see is that your old nature is only a private in the war against your new nature. Satan comes to the battle as an ally of the flesh and launches a massive attack. He is the general who marshals your sinful inclinations, exercises them mercilessly, and sends them out as a united front against the power of God in your life. Compare it to the following situation. Suppose that while a king is fighting to subdue his own mutinous subjects, some superior foreign troops should join with them and take command. Then the king no longer fights primarily against his subjects, but against a foreign power. You see the spiritual analogy: Even as the Christian is fighting against his own inner corruptions, Satan joins his power to the residue of the old nature and assumes command. It could be said that our sin is the engine, and Satan the engineer.
This knowledge should make every one of us diligent to keep our lusts unarmed – for they will be all too eager to declare their allegiance to Satan when he comes to tempt. Our own naked grace is no match in such a circumstance – as the odds are two to one against us. But, if we cling to God for strength and wisdom, then we will be able to deal mightily with this serpent and his lusty brood.” #William Gurnall.