Thank you for this question. I think it’s perhaps the most important question that we can ask as Christians. I don’t know which talk of Michael’s you’re referring to in particular, but I think I understand what you’re asking – that it’s one thing to say that being a Christian isn’t something we do, it’s something we are, but how does that translate into real life when we experience life at the levels of doing, thinking, and feeling!
I think the richest way into this question might be through reflecting on the Christian doctrine of adoption. Paul writes in Romans 8:15, “For you did not receive the spirit of slavery to fall back into fear, but you have received the Spirit of adoption as sons, by whom we cry, ‘Abba! Father!’” Paul echoes this teaching elsewhere (Ephesians 1:5 and Galatians 4:5-7) and we see it in Jesus’ own teaching as well: “I will not leave you as orphans; I will come to you." (John 14:18).
Adoption of course has to do with a change of legal status; it has to do with who we “are” – it’s a change at the level of identity, in terms of what family we belong to. An orphaned child goes from being without a family to belonging to one from the moment the adoption papers are signed. It’s a beautiful illustration of the Gospel because, for the orphaned child, the change of status does not depend on his or her actions, but rather wholly rests on the actions of the one doing the adopting, to bring the child into the family. We all are, by nature, alienated from God because of our sin, but God through Christ’s perfect life and alienation on our behalf on the cross, has adopted us into His family. This comes with a new identity – we belong to God, and we are “sons.” Tim Keller has helped me see that Paul’s language of “sons” and not “sons and daughters” is actually intentional and, far from being misogyny, reflects the very opposite; it would have been deeply encouraging to the first century woman, because at that time only the sons in the family had all of the rights to the inheritance. Paul is saying, when we become adopted by God, we are adopted with the full rights to the inheritance He promises us (Romans 8:17). What a thought.
But being adopted – having that change to our identity – should become then the source of the change in our lives, at the level of our doing, feeling, and thinking. Keller has a wonderful sermon illustration of this that I haven’t been able to find a link to, but I’ll share it here. He suggested we imagine what it would look like for a child from the streets to be adopted into the royal family. The moment the papers are signed, the child now belongs to this new family. There has been a change of status. However, it’s likely that the child will continue behaving in the same ways he had behaved on the streets – he might be used to scrounging around for food, never knowing when his next meal would come, so he might start doing that in the palace. Of course, it would be silly for him to do that now – he’s a prince (if he’s now a son of the king), with access to the king’s table! He’s taken care of, but his behaviour doesn’t change automatically because of his new status. If his new parents caught him scrounging in the palace pantry, they might sit down with him and say something like, “You know, you don’t need to scrounge for food like that any more – we’re taking care of you.” One might say, the task ahead for this child is now to “become who he now is” – to step into his new identity, and to change the way he lives. But the change will be driven by the security that the new identity brings.
So also, I think for the Christian, the source of real change in our lives will stem from our dwelling on, on a daily basis, the new secure identity we have in Christ. We don’t need to “scrounge” around desperately grasping for a sense of identity in the ways we did before we were believers, whether in relationships, success in our vocations, financial security, how we look, how fit we are, etc. We are taken care of now. What lies ahead of us is now to become who we are – to begin living out of our new identity in Christ. Practically, this might look like catching ourselves when we find ourselves going back to the ways we lived before, repenting and receiving God’s grace, and praying that God would assure us and remind us of the security we now have in Christ. From that point we must take small steps of obedience, by faith, trusting that God, by His Spirit, is committed now to making us into something new, and that “he who began a good work in you will bring it to completion at the day of Jesus Christ” (Phil 1:6).
In terms of resources, I think Keller has a chapter on identity in his book Making Sense of God that would have much of this content, but I also might just recommend a deep study on Romans 8; Martyn Lloyd Jones has a fantastic sermon series on Romans that has been a huge encouragement to my faith – you might check out his volume on Romans 8:5-17.
I hope that’s helpful David!