John Calvin on John 13:9

9. Lord, not my feet only. When Peter heard that he was ruined, if he did not accept the cleansing which was offered to him by Christ, this necessity proved, at length, to be a sufficient instructor to tame him. He therefore lays aside opposition and yields, but wishes to be entirely washed, and, indeed, acknowledges that, for his own part, he is altogether covered with pollution, and, therefore, that it is doing nothing, if he be only washed in one part. But here too he goes wrong through thoughtlessness, in treating, as a thing of no value, the benefit which he had already received; for he speaks as if he had not yet obtained any pardon of sins, or any sanctification by the Holy Spirit. On this account, Christ justly reproves him, for he recalls to his recollection what he had formerly bestowed on him; at the same time, reminding all his disciples in the person of one man, that, while they remembered the grace which they had received, they should consider what they still needed for the future.