[hosepipe]

[ "Simon changed his name to Peter, which means rock," he added. "Because Christ said he was the rock on which he would build the Church." ]

Almost correct....
"Because Christ said he was "A" rock on which he would build the Church."

[AnAmericanMother]

"Because Christ said he was "A" rock on which he would build the Church."

Not in the original Greek. Matthew 16:18: kai epi tauth th petra . It's sort of a double emphasis - tauth th means "this very same" - it's intensive. It wasn't "the".