Those who belong to Christ Jesus have crucified the sinful nature with its passions and desires. Since we live by the Spirit, let us keep in step with the Spirit.
What a phrase, "those who belong to Christ Jesus"! This is a statement about the identity of any Christian, and one that is important to remember and believe. We do not belong to our sin. We do not belong to our problems. We have someone we belong to, and it is Christ Jesus.
I was talking with Michael about the tense of the verb "have crucified," and it is the present perfect. According to the info I could find, that means that it happened in the past at a time that is not specifically mentioned, and it is usually used to emphasize the present effects of whatever thing that happened in the past.
That means the crucifixion of our sins has already happened. I don't think it means that the battle with sin is over, but I think it's interesting that he points back to a thing that happened in the past. Perhaps the crucifixion of our sin that happened when we first repented and believed in Jesus has cascading effects for the rest of our lives?
I think there is more meaning in the event itself. What does it mean that sin has been crucified? Wouldn't that mean it's dead? It doesn't seem to be dead. Perhaps it means that the death toll for sin has already rung, and once the Spirit of Christ is in us, it means certain eventual doom for any sin.
Perhaps the crucifixion is not finished, but is in the middle. Perhaps the old man is nailed to the cross, but he is still alive and writhing about in pain as he slowly dies.
The last part that was thought provoking to me was "we live by the Spirit." I think usually when I hear that phrase it has an ambiguous meaning that doesn't affect me much, but in the context of this verse I can see it as breath, as in "the Spirit is keeping us alive." It does make sense to stay with whatever thing is keeping you alive.