“As i stood there making a public profession as a Christian, my mind was full of lustful thoughts about a woman near me.” This was the confession of a man who later came to a deep experience with Christ and in so doing got the victory over his thoughts. Before his death he came to know the blessedness of those who are pure in heart.

The citadel of the mind is the hardest of all to capture for Christ, for the most vocal Christian can retreat within its walls and conjure up thoughts known only to himself—and to God.

The Bible is filled with warnings against the capacity for evil of the mind, often spoken of as the “heart,” the seat of emotions and thoughts. Jeremiah says: “The heart is deceitful above all things, and desperately corrupt; who can understand it?” (Jer. 17:9).

Because the cesspool of unholy thoughts can so easily be hidden beneath a cover of piosity, Christians often refuse to face up to it. “Let the wicked forsake his way, and the unrighteous man his thoughts” is often overlooked as a command for the Christian.

The Apostle Paul was keenly aware of the capacity of the mind for evil thoughts. The list of the sins of our lower nature is depressing, especially when we realize that they have their beginning in the mind: sexual immorality, impurity of mind, sensuality, worship of false gods, witchcraft, hatred, quarreling, jealousy, bad temper, rivalry, party spirit, envy, drunkenness, orgies, and so on. These evil things are present in our hearts in varying degree; in thinking on them there is sin, and in acting on them there is also sin.

Never have Christians needed this warning more than now. We live in a time when the eyes and ears are assailed by things that add fuel to the fires burning within. Yet because the fires cannot be seen we make a distinction between thinking and acting and the caldron seethes on.

Little wonder that the Apostle Paul, in pleading for lives dedicated completely to Christ, urges that we “let God remold [our] minds from within” (Rom. 12:2, Phillips).

David, in Psalm 51, speaks of this change of heart as a work of “creation.” In an agony of repentance he cries out: “Create in me a clean heart, O God, and put a new and right spirit within me” (Ps. 51:10).

The same thought is amplified by our Lord in a talk with the Pharisees: “For from within, out of the heart of man, come evil thoughts, fornication, theft, murder, adultery, coveting, wickedness, deceit, licentiousness, envy, slander, pride, foolishness. All these evil things come from within, and they defile a man” (Mark 7:21–23).

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What is needed is self-discipline by the help of the Holy Spirit. We are confronted with the kaleidoscopic passage of impure images across the retina of the mind, or with the burning fires of hate and jealousy. The images of the mind may also center on pride with all its ramifications of self-esteem and self-interest.

Against all these things there must be exercised a God-given discipline, the ability to turn from them to thoughts that are wholesome and constructive. Paul gives us the corrective: “Finally, brethren, whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is gracious, if there is any excellence, if there is anything worthy of praise, think about these things” (Phil. 4:8).

No two people look alike, nor do any two think alike. One may conjure up and dwell upon erotic thoughts, another may seethe with jealousy and envy, a third may be consumed with pride. All these things dishonor the Lord and should have no place in the mind of a Christian. That few of us have conquered this hidden evil is but an evidence of self-deception, and until cleansed by the indwelling Christ the sin remains a festering sore.

Aware of this seething caldron of unholy thoughts within, we too often resolve to abandon it and to turn our minds to other things—only to fail miserably. One day our Lord told of an unclean spirit going out of a man, finding no rest, and returning. There he found an empty heart—emptied of the evil spirit and devoid of a new guest. “Then he goes and brings with him seven other spirits more evil than himself, and they enter and dwell there; and the last state of that man is worse than the first. So shall it be also with this evil generation” (Matt. 12:45).

Nature abhors a vacuum, and this physical fact is carried over into the spiritual world. Jesus described the Pharisees as making clean the outside of the cup, “but inside you are full of extortion and wickedness.” Obviously, if the indwelling evil of the human heart is to be expelled, something must take its place. For this God has made full provision, the indwelling Spirit.

But before filling there must be cleansing. Just as the infilling is with a supernatural being, so the work of cleansing is a supernatural work, and here Calvary comes into focus. The writer of the Epistle to the Hebrews recalls the symbolic meaning of the Old Testament sacrifices: “Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins” (Heb. 9:22).

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However, we are no longer under the curse of the law, but are redeemed by the blood of Christ, the Son of God: “When Christ had offered for all time a single sacrifice for sins, he sat down at the right hand of God” (Heb. 10:12). The power of the blood of Calvary’s Cross is available to every sinner, to everyone whose heart is a seething caldron of things displeasing to God: “And the blood of Jesus his Son cleanses us from all sin.… If we confess our sin, he is faithful and just, and will forgive our sins and cleanse us from all unrighteousness” (1 John 1:7, 9).

The desperately wicked heart can be completely cleansed by the atoning blood of Christ, and it can be kept clean by the living presence of his Spirit in the heart. What is needed is regeneration, not reformation.

There must be a housekeeping, and there must be a new tenant. That God has provided the means and the Person is the hope of every sinner. And that this is obtainable by a single act of faith on our part is a marvelous provision of the gospel message.

The seething caldron of the human heart is the greatest killer of them all. It is the leprosy of sin, the cancer of lust, pride, and self; it is the heart disease of the soul.

But there is a cure. When the Holy Spirit takes possession, there is love, joy, peace, patience, self-control; and we are whole again.

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