Therefore = because of what has come before. Because God has saved us, gifted us with his Spirit, included the Gentiles, kept a remnant in Israel, and one day will turn even more hearts from Israel to the Messiah, we should transform our thinking and use our lives to serve Him (12:1-2)!
Part of this transformation process is making sure that we don’t think more highly of ourselves than we ought to, because each one of us has been gifted differently and we need to work together (12:3-8). Some of those gifts are listed here: prophecy, service, teaching, exhorting, giving, leading and showing mercy. Prophecy? If that is really about telling the future then why don’t we see more of it, or see the ones who try to engage in it be right more of the time!?!?!? Perhaps that gift was only for the apostolic age. However, there may be another way to look at it. A prophet in the Old Testament was not just a foreteller but a forth-teller. They challenged through God’s truth, and much of it was about the present rather than the future. In thinking about the difference in the church, a teacher can explain what the word of God says but may not be the best person to challenge others through the Word. That is more suited to one who has the gifting of a prophet.
A second way we are transformed is to show love without hypocrisy (12:9-21). While believers are gifted in particular ways, all are to show love. Love is a part of the community of faith. We should love enthusiastically. We are to hope with one another, support one another in troubles, and pray for one another. We should contribute to needs and show hospitality. We are to live in harmony with each other, not show favoritism, and not bearing grudges or seeking another’s harm.