John Calvin Commentary Romans 6:7

"for he that hath died is justified from sin." — Romans 6:7 (ASV)

For he who has died, etc. This is an argument derived from what pertains to death or from its effect. For if death destroys all the actions of life, we who have died to sin ought to cease from those actions which sin exercised during its life. Understand justified to mean freed or reclaimed from bondage; for just as a person who is absolved by a judge's sentence is freed from the liability of a charge, so death, by freeing us from this life, sets us free from all its functions.

But though no such example is found among people, there is still no reason why you should think that what is said here is a vain speculation, or lose heart because you do not find yourselves to be among those who have wholly crucified the flesh.

For this work of God is not completed on the day it is begun in us; instead, it progresses gradually, and through daily advances is brought by degrees to its completion.

So then, take this as the sum of the whole — “If you are a Christian, there must appear in you an evidence of fellowship with the death of Christ, the fruit of which is that your flesh is crucified together with all its lusts. But this fellowship is not to be considered as non-existent because you find that remnants of the flesh still live in you; rather, its increase ought to be diligently labored for until you arrive at the goal.”

It is indeed well with us if our flesh is continually mortified; nor is it a small attainment when its reigning power is taken away and wielded by the Holy Spirit.

There is another fellowship with the death of Christ, of which the Apostle often speaks, as he does in 2 Corinthians 4, that is, bearing the cross, which is also followed by joint participation in eternal life.