In chapter 16 of the Gospel of Matthew, Matthew, Jesus tells Peter: "You are Peter, and on this rock I will build my Church." The Roman Catholic Church has used this verse as support for its claim of papal supremacy. Protestants dispute the claim, in part on grounds that the word translated as “rock” might actually have meant “pebble”:
… In the original Greek the word translated as "Peter" is Πέτρος (Petros) and that translated as "rock" is πέτρα (petra), two words that, while not identical, give an impression of one of many times when Jesus used a play on words. … The traditional Catholic interpretation has therefore been that Jesus told Peter (Rock) that he would build his Church on this Peter (Rock).
… Some Protestant scholars disagree with this interpretation on the basis of the difference between the Greek words. In classical Attic Greek petros generally meant "pebble," while petra meant "boulder" or "cliff." Accordingly, taking Peter's name to mean "pebble," they argue that the "rock" in question cannot have been Peter, but something else, either Jesus himself, or the faith in Jesus that Peter had just professed. …
Wikipedia, Saint Peter (accessed Mar. 25, 2009; emphasis added).
Suppose that the author of the Greek text fully intended to use the term pebble and not rock. That would have Jesus saying, “upon this pebble I will build my church.”
When I read this, it immediately brought to mind the parable of the mustard seed in Matt. 13.31-32: "Though it is the smallest of all your seeds, yet when it grows, it is the largest of garden plants and becomes a tree ...." And then in Matt. 17.20, Jesus tells his disciples, “if you have faith as small as a mustard seed, you can say to this mountain, 'Move from here to there' and it will move. Nothing will be impossible for you.”
So maybe Jesus fully intended to call Peter a pebble, not a rock, and to declare that just as a tiny mustard seed grows into a tree, on such a pebble would his church be built.