New Bible Commentary
Eliakim stands in strong contrast to Shebna . . . Godward he is called ‘my servant’ (v.20; cf. ‘this steward’, v.15); manward, he will be ‘a father’ to his community (v.21) . . .
The opening words of v.22, with their echo of 9:6, emphasize the God-given responsibility that went with it [possession of the keys], to be used in the king’s interests. The ‘shutting’ and ‘opening’ mean the power to make decisions which no one under the king could override. This is the background of the commission to Peter (cf. Mt 16:19) and to the church (cf. Mt 18:18). (New Bible Commentary, Guthrie, D. & J.A. Motyer, eds., Grand Rapids, MI: Eerdmans, 3rd ed., 1970 [Reprinted, 1987, as The Eerdmans Bible Commentary], 603)
The phrase is almost certainly based on Is 22:22 where Shebna the steward is displaced by Eliakim and his authority is transferred to him. ‘And I will place on his shoulder the key of the house of David; he shall open, and none shall shut; and he shall shut, and none shall open.’ (This is applied directly to Jesus in Rev 3:7). (New Bible Commentary, Guthrie, D. & J.A. Motyer, eds., Grand Rapids, MI: Eerdmans, 3rd ed., 1970 [Reprinted, 1987, as The Eerdmans Bible Commentary], 837)
Theological Dictionary of the New Testament
In biblical and Judaic usage handing over the keys does not mean appointment as a porter but carries the thought of full authorization (cf. Mt. 13:52; Rev. 3:7) . . . The implication is that Jesus takes away this authority from the scribes and grants it to Peter. (J. Jeremias, in Theological Dictionary of the New Testament, Gerhard Kittel, abridgement of Geoffrey W. Bromiley, Grand Rapids, MI: Eerdmans, 1985, 440)
All these New Testament pictures and usages go back to a picture in Isaiah (Is 22:22) . . . Now the duty of Eliakim was to be the faithful steward of the house . . . So then what Jesus is saying to Peter is that in the days to come, he will be the steward of the Kingdom. (William Barclay, Gospel of Matthew, Philadelphia: Westminster Press, 1975, vol. 2, 144-145)
Isa 22:15 ff. undoubtedly lies behind this saying . . . The keys are the symbol of authority . . . the same authority as that vested in the vizier, the master of the house, the chamberlain, of the royal household in ancient Israel. Eliakim is described as having the same authority in Isaiah. (William F. Albright and C.S. Mann, Anchor Bible: Matthew, Garden City, NY: Doubleday, 1971, 196)
And what about the “keys of the kingdom”? . . . About 700 B.C. an oracle from God announced that this authority in the royal palace in Jerusalem was to be conferred on a man called Eliakim . . . (Isa. 22:22). So in the new community which Jesus was about to build, Peter would be, so to speak, chief steward. (F.F. Bruce, The Hard Sayings of Jesus, Downers Grove, IL: Intervarsity Press, 1983, 143-144)