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.

It may be objected that Jesus does not say ‘on you’ (i.e. on Peter personally) but on ‘this rock’ (indicating something associated with Peter.

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)