For I delight in the law of God, in my inner being,  but I see in my members another law waging war against the law of my mind and making me captive to the law of sin that dwells in my members. (ESV)
Did you know that there is a war going on and you are involved in it? There are many people who think that becoming a Christian is simply signing your name on the dotted line of eternal life and we just coast our way to eternity. The Apostle Paul knew something very different. He describes for us in these verses a very real war going on within him. This war is going on inside of you as well.
Paul begins by saying that in his inner being, he delights in the law of God. In verse 23 he refers to his inner being as the "law of my mind." This law within him delights in God's Law. This is because the Apostle Paul is a believer in Jesus Christ. He has been transformed by the power of God and been made a new creation in Christ Jesus.
As Paul told the Corinthians in 2 Corinthians 5:17, if anyone is in Christ he is a new creation. The old has gone. The new has come. Paul has a mind that is renewed. His mind, or inner being, is in agreement with the holy demands of a righteous God. But there is a problem. The members of his body don't always want to cooperate with the renewed mind.
The law of sin dwells in our body. It is going to fight against us when we decide that we want to follow God's commands. You have assuredly found this to be true in your walk with Christ. We are at war. The first step in winning this battle is to recognize that we are in one. We can be thankful that the Christ in us is greater than the law of sin in us. We can find victory in him alone.
You are at war. What have you done today to prepare yourself for battle. Perhaps a trip to Ephesians 6:10-18 would be a help to you. It is there that Paul describes the "Armor of God" that is available to you in this fight.