Legend says that as Shoeless Joe Jackson was leaving the courthouse during the trial of the Chicago Black Sox, as they were known, a young boy begged of him, “Say it ain’t so, Joe.”
Well, Jesus began to teach his disciples that the Son of Man must undergo great suffering, and be rejected by the elders, the chief priests, and the scribes, and be killed, and after three days rise again. He said all this quite openly.
And Peter said, “Say it ain’t so, Lord.” Maybe, Peter rebukes Jesus because he understands what Jesus is saying. Peter once told Jesus, “We have left everything to follow you.” A cross would mean no earthly kingdom. Instead of a sword (and we know that Peter owned a sword; a conceal and carry man), Jesus took up a cross.