John 13:8

Peter, however, cannot accept the disciple's attitude, but persists, Οὐ μὴ νίψῃς μου τοὺς πόδας εἰς τὸν αἰῶνα, “never shalt Thou wash my feet”. The εἰς τὸν αἰῶνα was prompted by the μετὰ ταῦτα. No future explanation can make this possible. Peter's humility is true enough to allow him to see the incongruity of Jesus washing his feet: not deep enough to make him conscious of the incongruity of his thus opposing and dictating to his Master. To this characteristic utterance Jesus, waiting with the basin, replies, ἐὰν μὴ νίψω σε … ἐμοῦ. Superficially these words might mean that unless Peter allowed Jesus to wash him, he could not sit at table with Him. But evidently Peter found in them a deeper significance, and understood them as meaning: Unless I wash you, you are outcast from my fellowship and cease to share in my kingdom and destiny. Here the symbolic significance of the eating together and of the washing begins dimly to appear. That Peter saw that this deeper meaning was intended appears from the eagerness of his answer.