How did Matthew 16:18 become important to claims of papal authority?

Matthew 16:18 is central to the Petrine theory, the foundational principle asserting the theological legitimacy of the papacy. In this passage, Jesus declares to the apostle St. Peter, "You are Peter, and upon this rock I will build my church," followed by the promise of the "keys to the kingdom of heaven" in verse 19.123

Roman Catholic teaching interprets these verses as Christ’s direct establishment of Peter as the prince of the Apostles and the visible head of the church. This authority is understood not merely as an honorary title but as a mandate of true jurisdiction. Furthermore, the church maintains that this Petrine primacy was intended to pass in perpetuity to Peter’s successors, identified as the bishops of Rome.13

By linking the office of the pope to this scriptural foundation, the church establishes the papacy as a continuous line of apostolic succession, providing the theological basis for the pope's role as the chief bishop and ultimate authority in matters of faith and morals.13