"We have an obligation..." (Romans 8:12)

1. Paul is serious about the need for us to put into effect the new life God gives us. Our response is not optional; it is necessary.
2. However, this response is itself empowered by the Spirit. We cannot stop committing sins in our own power; it can only be done “by the Spirit.”
3. Paul never suggests that the inheritance of future life requires that we stop sinning altogether. What he demands in this verse is clear, long-term, progress in becoming less like the world (“the flesh”) and more like Christ.

- NIV Application Commentary

“Looking back now over the first half of Romans 8, we have seen something of the multiple ministries of the Holy Spirit. He has liberated us from the bondage of the law (2), while at the same time he empowers us to fulfil its just requirement (4). We now live each day according to the Spirit and set our minds on his desires (5). He lives in us (9), gives life to our spirits (10), and will one day give life to our bodies too (11). His indwelling obliges us to live his way (12), and his power enables us to put to death our body’s misdeeds (13). He leads us as God’s children (14) and bears witness to our spirit that this is what we are (15–16). He himself is also the foretaste of our inheritance in glory (17). It is his indwelling which makes the fundamental difference between Romans 7 and Romans 8.”

- The Bible Speaks Today Commentary