[BipolarBob]

“you are rock and on this rock I will build My Church”.

Rock was talking to rock. There are two rocks (one lower case and the other upper case) involved. There is more than one way to interpret this sentence from the words alone. You (your Church) picks the one way that takes away glory from Jesus (The Rock) and gives it to Peter (rock).
If you think Martin Luthers attempted reformation of the RCC was upsetting, then when Jesus comes back to finish the job there will be weeping, wailing and gnashing of teeth.

[Cronos]

There was one word rock, declined for locative — petros in locative is petra in Koine Greek

[WVKayaker]

BB, shake the dust...

Look! Squirrel! (pay no attention to the man behind the curtain TRUTH!)

[Cronos]

Remember as I've said above -- there is the case of locative, so this is one word but in nominative and locative: "you are {nominative case} and on this {locative case}...."

you can replace this with table :) and it is "mensa pones super mensam es" -- you see the declension ending of -m?