Jesus did not wash the disciple's feet for fleshly sanitation, if so he would have done it BEFORE the Seder Meal. "He got up from the meal, took off his outer clothing, and wrapped a towel around his waist". John 13:4. He did it in the Seder as a leader washing not himself, but those around him, washing them..we must do the same with whom we live. Judas who betrayed him was washed by Jesus with the others.