What is substitution in the teaching about being crucified with Christ?
Substitution is God’s provided loophole: because the law requires every sinner to die, Christ died in the believer’s place. God also reckons believers as crucified with Christ, so they experience that same death in Him, satisfying the law’s demand while being put to death in God’s mind.
Les teaches that along with all the other things God has done on our behalf, He has reckoned us as crucified with Christ. Crucifixion can only do one thing—put to death—so believers have been put to death in the minds of God. This goes back to God’s first law to Adam and Eve, “The day that thou eatest thereof, thou shalt surely die,” and also to Ezekiel, “The soul that sinneth shall surely die.” Since the law determines every human being is a sinner because we are sons of Adam, every human being has to die. Les calls God’s provision a loophole: He died in our place. Yet believers still have to experience that same death He experienced in the person of Christ, and that is called substitution. The context then points to Romans 6, verse 6.
Knowing this, that our old man is crucified with him, that the body of sin might be destroyed, that henceforth we should not serve sin.