Jesus said, “If any man would come after me, let him deny himself and take up his cross and follow me” (Mark 8:34). This is Jesus’s figure of speech for self-denial. Every disciple of Jesus is to ‘behave like a condemned criminal and carry his cross to the place of execution.’ Paul uses this metaphor in Galatians: “Those who belong to Christ Jesus have crucified the flesh with its passions and desires” (Gal.5:24). “We must not only take up our cross and walk with it, but actually see that the execution takes place. We are actually to take the flesh, our willful and wayward self, and (metaphorically speaking) nail it to the cross. This is Paul’s graphic description of repentance, of turning our back on the old life of selfishness and sin, repudiating it finally and utterly.”

What does this mean? The old nature, our willful and wayward self, our former life without Christ, what Paul calls ‘the flesh’, is to be mortified or crucified.

First, a Christian’s rejection of his old nature is to be pitiless. Crucifixion in the Graeco-Roman world was not a pleasant form of execution, nor was it administered to nice or refined people; it was reserved for the worst criminals, which is why it was such a shameful thing for Jesus Christ to be crucified. If, therefore, we are to ‘crucify’ our flesh, it is plain that the flesh is not something respectable to be treated with courtesy and deference, but something so evil that it deserves no better fate than to be crucified.

Secondly, our rejection of the old nature will be painful. Crucifixion was a form of execution ‘attended with intense pain’. And which of us does not know the acute pain of inner conflict when ‘the fleeting pleasures of sin’ are renounced?

Thirdly, the rejection of our old nature is to be decisive. Although death by crucifixion was a lingering death, it was a certain death. Criminals who were nailed to a cross did not survive. John Brown draws out the significance of this fact for us: ‘Crucifixion…produced death not suddenly but gradually….True Christians….do not succeed in completely destroying it (that is, the flesh) while here below; but they have fixed it to the cross, and they are determined to keep it there till it expire.’ When we came to Jesus Christ, we repented. We ‘crucified’ everything we knew to be wrong. We took our old self-centered nature, with all its sinful passions and desires, and nailed it to the cross. And this repentance of ours was decisive, as decisive as a crucifixion. So, Paul says, if we crucified the flesh, we must leave it there to die. We must renew every day this attitude towards sin of ruthless and uncompromising rejection.

So widely is this biblical teaching neglected, that it needs to be further enforced. The first great secret of holiness lies in the degree and the decisiveness of our repentance. If besetting sins persistently plague us, it is either because we have never truly repented, or because, having repented, we have not maintained our repentance. It is as if, having nailed our old nature to the cross, we keep wistfully returning to the scene of its execution. We begin to fondle it, to caress it, to long for its release, even to try to take it down again from the cross. We need to learn to leave it there. When some jealous, or proud, or malicious or impure thought invades our mind we must kick it out at once. It is fatal to begin to examine it and consider whether we are going to give in or not. We have declared war on it; we are not going to resume negotiations. We have settled the issue for good; we are not going to reopen it. We have crucified the flesh; we are never going to draw the nails.

(Ted Schroder, John Stott: A Summary of his teaching, p.108f.)