At Works, 5.81 Ruskin adds that Raphael 's Cartoon of The Charge to Peter is a lie to serve the 'papal heresy of Petric supremacy' because it puts all the apostles in the picture in the background as witnesses. Ruskin suggests that this misrepresents the account in St. John's Gospel Chapter 21.
However Shearman, Raphael's Cartoons, points out that the cartoon refers also to St. Matthew's Gospel Chapter 16. In the cartoon St. Peter is holding keys, and these may be more than mere conventional identifiers, but a direct reference to the verse in Matthew: 'And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven.'
That text is important in justifying papal claims, and that is part of the reason for the iconographic scheme of the picture and also, no doubt, part of the reason that the Protestant Ruskin dismisses it as a 'mere lie'.