Fulfilling the Righteous Requirement of the law
For what the law was powerless to do in that it was weakened by the sinful nature, God did by sending his own Son in the likeness of sinful man to be a sin offering. And so he condemned sin in sinful man, in order that the righteous requirements of the law might be fully met in us, who do not live according to the sinful nature but according to the Spirit. Romans 8:3,4
There are two distinctively different ways of understanding 8:4 ‘in order that the righteous requirements of the law might be fully met in us, who do not live according to the sinful nature but according to the Spirit’.
The first puts its emphasis on our justification. The NIV makes ‘requirements’ plural but Paul made it singular. If it was meant to be plural Paul would have been particularly thinking of the way the Spirit enables Christians to obey the law, but ‘requirement,’ singular, sees the commandments of the moral law as a whole. When this is combined with ‘fully met’ being passive, Paul’s emphasis is that God in Christ has fulfilled the entirety of the law’s demand on our behalf. The only beneficiaries of Christ’s obedience are those marked out by their justification and their having the indwelling Spirit. As we live in the Spirit we are identified as those who are ‘in Christ,’ in the one who Himself completely satisfied the Father’s demand for holiness as expressed in the law and who bore the penalty of the broken law on behalf of those who have faith in Him. So the first emphasis is on our justification.
The second understanding of 8:4 puts the verse’s emphasis on our sanctification. If God’s purpose in sending His Son was limited to our justification, then the conditional clause ‘who do not live according to the sinful nature but according to the Spirit’ (8:4) is unnecessary. God wants the requirement (singular) of the law, the commandments of the moral law viewed as a whole, ‘fulfilled’ (obeyed, not satisfied) in the lives of His people. Jesus Himself spoke of fulfilling the law (Matthew 5:17) and Paul will write later of love of neighbour as the chief ‘fulfilment of the law’ (Romans 13:8-10). The law can only be fulfilled in those ‘who do not live according to the sinful nature but according to the Spirit’ (8:4). The flesh renders the law impotent but the Spirit empowers us to obey it. Holiness is the ultimate purpose of the incarnation and the atonement. The end God had in mind in sending His Son was not just our justification (through freedom from the condemnation of the law) but also our holiness (through obedience to the commandments of the law). Law-obedience is not the ground of our justification but it is the fruit of it. Our freedom from the law (7:4,6; 8:2) is not freedom to disobey it.
Paul’s purpose in 8:1-4 is to show how we are no longer condemned. His reason is that we have, in Christ, effectively fulfilled God’s demand expressed through the law. This happens as we walk in the Spirit. If Paul is referring to the way Christians ‘actively’ fulfil the law in their own lives, then living in the Spirit is the cause and power of this obedience. If Paul is referring to the way Christians ‘passively’ fulfil the law in their own lives, then they show the reality of what Christ has done for them by living in the Spirit. Either way, the people in whom the law is fulfilled are those who live in the realm of the Spirit.