"Where in scripture do you find a direct, in context quote that allows for this? "
"I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven" [Matt 16:19].
BIBLE COMMENTARY ON "KEYS" OF MATTHEW 16:19
M. Eugene Boring (Disciples of Christ), commenting on the "keys of the kingdom of heaven," "binding" and "loosing" from Matthew 16:19 --
"The 'kingdom of heaven' is represented by authoritative teaching, the promulgation of authoritative Halakha that lets heaven's power rule in earthly things...Peter's role as holder of the keys is fulfilled now, on earth, as chief teacher of the church....The keeper of the keys has authority within the house as administrator and teacher (cf. Isa 22:20-25, which may have influenced Matthew here). The language of binding and loosing is rabbinic terminology for authoritative teaching, for having the authority to interpret the Torah and apply it to particular cases, declaring what is permitted and what is not permitted. Jesus, who has taught with authority (7:29) and has given his authority to his disciples (10:1, 8), here gives the primary disciple the authority to teach in his name -- to make authoritative decisions pertaining to Christian life as he applies the teaching of Jesus to concrete situations in the life of the church." (Boring, page 346)
Francis Wright Beare (Presbyterian/Reformed) -- "The 'keys' are probably not to be understood as entrance keys, as if to suggest that Peter is authorized to admit or to refuse admission, but rather to the bundle of keys carried by the chief steward, for the opening of rooms and storechambers within the house -- symbols of responsibilities to be exercised within the house of God (cf. Mt 24:45, etc.). 'Bind' and 'loose" are technical terms of the rabbinic vocabulary, denoting the authoritative declaration that an action or course of conduct is permitted or forbidden by the Law of Moses." (Beare, page 355-356)
Eduard Schweizer (Presbyterian/Reformed) -- "In Jewish interpretation, the key of David refers to the teachers of the Law (exiled in Babylon); according to Matthew 23:13, the 'keys of the Kingdom of heaven' are in the hands of the teachers of the Law. A contrast is here drawn between them and Peter. He is thus not the gatekeeper of heaven, but the steward of the Kingdom of heaven upon earth. His function is described in more detail as 'binding and loosing' ....the saying must from the very outset have referred to an authority like that of the teachers of the Law. In this context, 'binding" and 'loosing' refer to the magisterium to declare a commandment binding or not binding....For Matthew, however, there is only one correct interpretation of the Law, that of Jesus. This is accessible to the community through the tradition of Peter...Probably we are dealing here mostly with teaching authority, and always with the understanding that God must ratify what Petrine tradition declares permitted or forbidden in the community." (Schweizer, page 343)
R.T. France (Anglican/Protestant Evangelical) -- "The terms [binding and loosing] thus refer to a teaching function, and more specifically one of making halakhic pronouncements [i.e. relative to laws not written down in the Jewish Scriptures but based on an oral interpretation of them] which are to be 'binding' on the people of God. In that case Peter's 'power of the keys' declared in [Matthew] 16:19 is not so much that of the doorkeeper... but that of the steward (as in Is. 22:22, generally regarded as the Old Testament background to the metaphor of keys here), whose keys of office enable him to regulate the affairs of the household." (R.T. France, as cited in Butler/Dahlgren/Hess, page 54)
Joachim Jeremias in an extended passage from Kittel's Greek standard TDNT -- "...the key of David is now (3:7) the key which Christ has in His hands as the promised shoot of David. This is the key to God's eternal palace. The meaning of the description is that Christ has unlimited sovereignty over the future world. He alone controls grace and judgment. He decides irrevocably whether a man will have access to the salvation of the last age or whether it will be witheld from him...Materially, then, the keys of the kingdom of God are not different from the key of David...This is confirmed by the fact that in Mt. 16:19, as in Rev. 3:7, Jesus is the One who controls them. But in what sense is the power of the keys given to Peter? ....the handing over of the keys is not just future. It is regarded as taking place now... There are numerous instances to show that in biblical and later Jewish usage handing over the keys implies full authorisation. He who has the keys has full authority. Thus, when Eliakim is given the keys of the palace he is appointed the royal steward (Is. 22:22, cf. 15). When Jesus is said to hold the keys of death and Hades (Rev. 1:18) or the key of David (3:7), this means that He is, not the doorkeeper, but the Lord of the world of the dead and the palace of God...Hence handing over the keys implies appointment to full authority. He who has the keys has on the one side control, e.g., over the council chamber or treasury, cf. Mt. 13:52, and on the other the power to allow or forbid entry, cf. Rev. 3:7...Mt. 23:13 leads us a step further. This passage is particularly important for an understanding of Mt. 16:19 because it is the only one in the NT which presupposes an image not found elsewhere, namely, that of the keys of the kingdom (royal dominion) of God...Mt. 23:13 shows us that the scribes of the time of Jesus claimed to possess the power of the keys in respect of this kingdom...They exercised this by declaring the will of God in Holy Scripture in the form of preaching, teaching and judging. Thereby they opened up for the congregation a way into this kingdom...by acting as spiritual leaders of the congregation....As Lord of the Messianic community He thus transferred the keys of God's royal dominion, i.e. the full authority of proclamation, to Peter...In Rabb. lit. binding and loosing are almost always used in respect of halakhic decisions...The scribe binds (declares to be forbidden) and looses (declares to be permitted)...In Mt. 16:19, then, we are to regard the authority to bind and to loose as judicial. It is the authority to pronounce judgment on unbelievers and to promise forgiveness to believers." (Jeremias from Kittel/Bromiley, Theological Dictionary of the New Testament, volume 3, page 748-751)
The older The Interpreter's Bible -- "19. The keys of the kingdom would be committed to the chief steward in the royal household and with them goes plenary authority. In Isa. 22:22 the key of the house of David is promised to Eliakim. According to Paul, Jesus is the only foundation (I Cor. 3:11), and in Rev. 1:18; 3:7, Jesus possesses the key of David and the keys of death and Hades. But in this passage Peter is made the foundation (cf. Eph. 2:20, where the Christian apostles and prophets are the foundation and Christ is the cornerstone) and holds the keys. Post-Apostolic Christianity is now beginning to ascribe to the apostles the prerogatives of Jesus (cf. 10:40). In rabbinical language to bind and to loose is to declare certain actions forbidden or permitted [a Jewish source Terumoth 5:4 is quoted]...Thus Peter's decisions regarding the O.T. law (e.g., in Acts 10:44-48) will be ratified in heaven." (George Arthur Buttrick, et al The Interpreter's Bible [Abingdon Press, 1951], volume 7, page 453)
Willoughby C. Allen, in a still older commentary that interprets the "rock" of Matthew 16:18 as the "revealed truth" of the Messiahship of Christ, nevertheless writes in his The International Critical Commentary --
"The figure of the gates of Hades suggests the metaphor of the keys. There were keys of Hades, Rev 1:18; cf. 9:1; 20:1. The apocalyptic writer describes the risen Christ as having the keys of Hades, i.e. having power over it, power to enter it, and power to release from it, or to imprison in it. In the same way, 'the kingdom of the heavens' can be likened to a citadel with barred gates. He who held the keys would have power within it, power to admit, power to exclude. In Rev 3:7 this power is held by Christ Himself [quotes Rev 3:7]...The words are modelled on Is 22:22, and express supreme authority. To hold the keys is to have absolute right, which can be contested by none...It would, therefore, be not unexpected if we found the Messiah or Son of Man described as having the keys of the kingdom of the heavens. This would imply that He was supreme within it. But it is surprising to find this power delegated to S. Peter...To S. Peter were to be given the keys of the kingdom. The kingdom is here, as elsewhere in this Gospel, the kingdom to be inaugurated when the Son of Man came upon the clouds of heaven. If S. Peter was to hold supreme authority within it, the other apostles were also to have places of rank...To 'bind' and to 'loose' in Jewish legal terminology are equivalent to 'forbid' and 'allow,' to 'declare forbidden' and to 'declare allowed'...The terms, therefore, describe an authority of a legal nature. If he who has the keys has authority of an administrative nature, he who binds and looses exercises authority of a legislative character....Further, the position of v. 18, with its description of the Church as a fortress impregnable against the attacks of evil (the gates of Hades), suggest irresistibly that 'the keys of the kingdom' mean more than power to open merely, and imply rather authority within the kingdom. And this is confirmed by the 'binding' and 'loosing' which immediately follow...What were the keys thus given? Even if we identify the kingdom with the Church, it is not entirely satisfactory to suppose that the Lord simply foretold that S. Peter was to take a prominent part in the work of opening the door of faith to the Gentiles. His share in that work, though a great, was not an exclusive one....The motive must have been to emphasise the prominence of S. Peter in the Christan body as foretold and sanctioned by Christ Himself...They [the apostles] had left all to follow Christ; but when He sat on the throne of His glory they would sit on twelve thrones, judging the twelve tribes of Israel, 19:18. And amongst them Peter was pre-eminent. He was protos, 10:2." (Allen, The International Critical Commentary [orig 1909, 1985], page 176ff)
Raymond Brown and John Reumann suggest other possible meanings --
"What else might this broader power of the keys include? It might include one or more of the following: baptismal discipline; post-baptismal or penitential discipline; excommunication; exclusion from the eucharist; the communication or refusal of knowledge; legislative powers; and the power of governing." (Brown, Reumann, et al Peter in the New Testament, page 97)
Source: http://www.bringyou.to/apologetics/PeterRockKeysPrimacyRome.htm