A father and a son were once guests of Imam Ali (A.S.). As they arrived, Imam (A.S.) received them warmly and arranged for their comfortable accommodation. In a room where they were seated, Imam (A.S.) sat opposite to them, engaging them in a friendly conversation. And then it was time for the meal. After food had been served and eaten, Qambar, Imam's servant, brought a basin and a pitcher full of water for washing the guest's hands. Imam (A.S.) took the pitcher himself and asked the father to extend his hands so that he would pour the water.
"How is it possible that my Imam serves me? It should be other way," the guest said.
Imam Ali (A.S.) said: "Here is your brother in faith, eager to serve his brother and to earn the pleasure of Allah. Why do you prevent him?"
But the guest hesitated. Finally Imam (A.S.) said: "As your Imam, I request that you allow me the honor of this service."
And when the guest complied, Imam (A.S.) said: "Let your hands be washed thoroughly. Do not hasten, thinking that I should be relieved of this duty early."
When it was the son's turn, Imam (A.S.) instructed his own son Muhammad Ibn Hanafiyyah, to hold the pitcher and wash the guest's hands. Looking at his son, Imam (A.S.) said:
I washed your father's hands. My son washed your hands. If your father had not been my guest today, I would have washed your hands myself. But Allah loves to see that when a father and a son are present in a place, the father enjoys a privilege and a priority.
source : sibtayn
