but be transformed by the renewing of your mind,
so that you may prove what the will of God is,
that which is good and acceptable and perfect. (NASB)
The second half of this verse sets forth the purpose for the renewing of our mind—to discern the will of God.What does Paul mean by “prove” the will of God?
Prove (dokimazo) in this verse means to discern or understand the will of God, and it also has the sense of approving or agreeing with what God desires. Once we understand what God wants, we will want to do it, because it is good (as God is good), acceptable (pleasing to God), and perfect (mature, not sinless).
The believer’s ability to discern the will of God is significant for Paul’s argument in Romans, as Douglas Moo points out. Because Paul taught Jewish converts to Christ that they are no longer under the law (6:14), his Jewish opponents attacked his gospel for promoting lawlessness. So here in 12:2 Paul responds that believers in Christ do not need the Old Testament law to tell them how to live. In the new covenant, God renews minds and hearts with a desire for godliness:
Moo points out that those who trust in Christ are now under “the law of Christ” (Galatians 6:2). Our “law” consists of the standards for conduct Jesus taught about the will of God. We also obey his apostles, who expanded on Jesus’ teaching in their epistles to the churches. Because Paul was confident that the Holy Spirit would renew believers’ minds as they were instructed by the word of God, he trusted they would know how to do the will of God.
Here is how Moo puts it: “Paul’s vision, to which he calls us, is of Christians whose minds are so thoroughly renewed that we know from within, almost instinctively, what we are to do to please God in any given situation.” The renewed mind filled with God’s word has replaced OT law as the believer’s guide for conduct.The indispensable word of God
Christians of all levels of maturity need to stay in the word of God. Discernment and obedience follow as the word and the indwelling Holy Spirit to do their work. On the other hand, when Christians cease reading the word, the result is usually a gradual conforming to ideologies of the world Paul warns about in the first line of this verse. Community is also important; Christians learn best when they serve, exhort, and teach one another, as we’ll see later in this chapter.
The last word goes to R. C. Sproul: “If you want to live a godly life, then it is indispensable to your spiritual growth that you dig into the Scriptures deeply, to understand what God is revealing. This is part of the sacrifice of the Christian life.”