16:18 And I tell you that you are Peter, and on this rock I will build my church, and the gates of Hades will not overpower it.

1. Some think that the rock is Peter himself.  In support of this interpretation is the fact that what Jesus says is in the singular, and must have been addressed to Peter himself (even if it also had a wider application).  There is an interesting comparison with the Midrash on Isa 51:1, where God says of Abraham: ‘Behold, I have found a rock on which I can build and base the world. Therefore he called Abraham a rock’ (SB, 1, p. 733, cited by NBD).’

In wider application, this saying (according to this interpretation) would apply to the first apostles and prophets, on whose foundation the church was built.

William Johnstone, a spokesman for ‘Catholic Voices’ and Duncan Boyd, representing the Protestant Truth Society, discussed this passage:

William’s (and presumably the Catholic church’s) argument relied in part on the assumption that Jesus spoke these words in Aramaic, in which language the word for ‘Peter’ and ‘rock’ would have been the same (cephas). But, as Duncan pointed out, it is not at all certain that these words were spoken by Jesus in Aramaic. And, in any case, this saying is recorded in Scripture not in Aramaic, but in Greek. Two different Greek words are used, ‘petros’ and ‘petra’, weakening the idea that they both have the same referent. In any case, Jesus does not say, “on you will I build my church”, strongly suggesting that the church is to be built, not on Peter personally, but on the confession he has just made, “You are the Christ, the Son of the living God”, which would be echoed by all the apostles and their followers.

When Jesus says that “the gates of Hades will not overcome [his] church”, this means, according to William, that the church has infallible authority. If the church could err, then this could scarcely be said of it. But, as Duncan pointed out, the Catholic church can and has erred, even in some of its most authoritative pronouncements (such as Papal bulls advocating anti-semitism). Within the pages of the New Testament itself, we find local churches exhibiting various forms of error (just think of the 7 churches in Revelation 2-3). Jesus expression here means that the church will not die, even though he himself and also Peter would die.

2. Others think that the rock is Peter’s confession of Jesus as Messiah.  This interpretation pays due attention to the context, in which Peter’s confession is pivotal.  The church is built on the rock of apostolic confession (cf. Eph 2:20).  ‘The familiar “You are Peter, and on this rock I will build my church” may mean not that the rock is Peter the person but that it is Peter confessing Jesus as “the Christ, the Son of the living God.” In this case Christ, whom Peter is confessing, is the important one, not Peter himself, and Christ becomes the foundation of the church as he is thus confessed’ (IVP Commentary on Eph 2:19-22).‘Now that someone has been found who is prepared to confess Jesus as what he really is, and not try to fit him into some inherited framework, a start can be made with forming the community of true disciples who will carry on Jesus’ mission after his departure.’ (HSB)

Murray Harris, who favours this interpretation, invites us to note that ‘the earliest and foundational confession made by Christians was in fact “Jesus is the Messiah” (see Acts 18:5, 28; cf. Acts 2:36; 9:22; 17:3).’ (Navigating Tough Texts)

3. Michael Heiser suggests that ‘this rock’ is the very ground they were standing on.  Jesus and his disciples were at this time in Caesarea Philippi, near the foot of Mount Hermon.  In the OT, this region was known as Bashan, and was believed to be the gateway to the underworld, Sheol/Hades, the realm of the dead and of demons.  Heiser add that the phrase ‘the gates of hell shall not prevail against it’ suggests on onslaught on the church by the forces of evil.  But, he writes, the word ‘against’ is not present in the Greek.  ‘Translating the phrase without it gives it a completely different connotation: “the gates of hell will not withstand it.  It is the Church that Jesus sees as the aggressor. He was declaring war on evil and death. Jesus would build His Church atop the gates of hell—He would bury them.’ (I Dare You Not To Bore Me With The Bible)