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John 13:9–11 Simon Peter said to Him, “Lord, not my feet only, but also my hands and my head!” Jesus said to him, “He who is bathed needs only to wash his feet, but is completely clean; and you are clean, but not all of you.” For He knew who would betray Him; therefore He said, “You are not all clean.” (NKJV)
The foot washing is for “he who is bathed,” that is, for believers (not Muslims.)
I see you beat me to it, but you’re 100% correct. The foot washing was for believers, and it demonstrated an essential Christian concept. If it was just about being humble, then why wouldn’t Christ give them all baths? That would be even more humble than washing just their feet, right? Ah! But it wasn’t about being humble! It was about about showing them that even though they had been completely washed when they accepted Christ, they still needed to be touched up from time to time. An unbeliever who has never had a spiritual bath does not need their spiritual feet washed.
Believers like Judas?