We are also liable to temptation from the world without, and from the corruptions of our own hearts within. "They that will be rich fall into temptation and a snare." The riches, honors, pleasures, and fashions, of this world, are great enemies to serious piety. "Every man is tempted when he is drawn away of his own lusts and enticed." Remaining corruption is the sorest evil that besets the Christian. The temptations of Satan alone would be light, in comparison with the inward conflict he is compelled to maintain against the lusts of his own heart. But the devil makes use of both these sources of temptation to accomplish his ends. The former he uses as outward enticements, and the latter act as traitors within. Thus you may generally find a secret alliance between the arch deceiver and the corruptions of your own heart. It is not sin to be tempted: but it is sin to give place to temptation. "Neither give place to the devil." The heart is very properly compared to a castle or fort. Before conversion it is in the possession of the great enemy of souls, who has fortified himself there, and secured the allegiance of all our moral powers. But when Jesus enters in, he "binds the strong man armed," and takes possession of the heart himself. Yet Satan, though in a measure bound, loses no opportunity to attempt regaining his lost dominion. Hence we are directed to "keep the heart _with all diligence_." Now we know how a castle, fort, or city, is kept in time of war. The first thing done is to _set a watch_, whose business is to keep constantly on the look out, this way and that way, to see that no enemy is approaching from without, and no traitor is lurking within. Hence we are so frequently exhorted to _watch_. "Watch and pray, that ye enter not into temptation." "Take heed, watch and pray; for ye know not when the time is." "And what I say unto you, I say unto all, Watch." "Watch ye, stand fast in the faith, quit you like men, be strong." "Continue in prayer, and watch _in_ the same, with thanksgiving." "Praying always, with all prayer and supplication in the Spirit, and _watching thereunto_ with all perseverance." "Let us watch and be sober." "Watch then _in all things_." "Watch _unto_ prayer." "Blessed is he that _watcheth_, and keepeth his garments, lest he walk naked, and they see his shame." "Set a watch, O Lord, before my mouth; keep the door of my lips." If we were in a house surrounded by a band of robbers, and especially if we knew there were persons in it who held a secret correspondence with them, we should be continually on our guard. Every moment we should be _watching_, both within and without. But such is the state of our hearts. Surely, no ordinary danger would have called forth from our Lord and his apostles such repeated warnings. We are directed to watch in _all things_. Keep a continual guard over your own heart, and over every word and action of your life. But there are particular seasons when we should set a _double watch_.