In this passage Isaiah denounces one Shebna, the prime minister (“who is master of the household,” Is 15), and predicts his replacement by Eliakim. The passage is notable for its use of the “key” taken up in the Gospel today, the Tu es Petrus saying.
Slightly different selections of verses from this psalm are used on the fifth and seventeenth Sundays of the year in series C. Today’s refrain (“Lord, your love is eternal”) suggests that God’s purposes are not defeated by the infidelity of his human instruments. God can replace a faithless agent with another who is faithful to him.
This magnificent doxology comes at the end of Paul’s discussion of Israel’s place in salvation history. Biblical theology is an attempt to reflect on the ways of God in salvation history. This is precisely what Paul has been doing in Rm 9-11.
But the biblical theologian must always confess the inadequacy of his or her work.
The riches and wisdom of knowledge of God are always too deep to penetrate, God’s judgments and ways are unsearchable. No theologian has ever known the mind of the Lord. No theology, however venerable, can claim to be absolute.
There comes a time when the theologian must lay down the pen and confess the relativity of all his or her formulations. Theology is therefore always subject to change. And theology is best done in the context of liturgy. It must be doxological.
Matthew has introduced considerable alterations into his Marcan source. The words “Son of the living God” are added to Peter’s confession. In Mark, Jesus almost ignores Peter’s confession and enjoins the disciple to silence. He then proceeds at once to speak of the necessity of his passion. Peter protests and is met by the rebuke “Get behind me, Satan.” (Mt 16:23)
Matthew has placed the prediction of the passion, Peter’s objection, and Jesus’ rebuke in a separate pericope following the confession. Instead, Jesus pronounces Peter blessed and gives him the name Peter, “Rock.”
Then comes a series of promises: the building of the church on the foundation of Peter; the assurance that the powers of death shall not prevail against that church; the promise of the keys; and the saying of the binding and loosing.
There seems to be a growing consensus that the original situation of these words to Peter was not in the earthly life of Jesus but in a post resurrection setting; that the whole passage, Mt 16:17-19, enshrines very early material going back to the Aramaic-speaking Church; and that the Rock on which the church is to be built is Peter himself, not his faith, as some patristic and most Reformation exegesis has supposed.
But there is division among exegetes along confessional lines over the question of the continuation of Peter’s function in the church.
Protestant exegesis sees the fulfillment of the saying about the Rock in the once-and-for-all role that played such a large part in the foundation of the church after the first Easter and resurrection appearances (Cullmann), and sees the power of the keys and of binding and loosing as continued in the church as a whole, though capable of being entrusted to particular officers by the community (Marxsen).
Anglican exegetes tend to agree with the Orthodox that the power of the keys and of binding and loosing is shared by the whole episcopate, though many of them would be prepared to allow the Bishop of Rome a special place in this collegial office. Catholic scholars naturally maintain that the Petrine office is vested in the papacy.
Nonetheless, it is significant that on all sides there is growing Christian awareness that one aspect of the Petrine office—witness to the resurrection—belongs to the events of the Christian beginnings and is therefore inalienable. At the same time, its other aspects—keys, binding and loosing—continue in the church. This continuity is a sign of the faithfulness of God.