Many regard Rom 1:17, which contains Paul's own declarative statement and its scriptural proof from Hab 2:4, as the thesis of Romans. How the passage is read therefore determines how the whole letter is interpreted. The traditional Lutheran understanding is that the passage introduces and provides a framework for the doctrine of justification by faith, where the 'righteous one' in the Habakkuk citation (Rom 1:17b) represents a person who was ungodly but is now justified or declared righteous through his or her own faith. This understanding has been challenged by some who have offered a christological reading where the person of the citation is taken to be Christ, hence one's justification depends chiefly on Christ's faithfulness. The study in this book adjudicates mainly between these two interpretative categories through thorough and comprehensive exegetical considerations of internal texts and comparative analyses of scriptural and Second Temple Jewish backgrounds. The result shows the internal coherence and cogency of the christological interpretation while acknowledging the validity of the traditional-Lutheran understanding of the passage.