Imam Hasan (a.s.) and Amr Bil Maroof (Enjoining good)
An old man sat to do his Wudhu / Wuzu (Ablution). But his Wudhu was not correct. Imam Hasan (a.s.) and Imam Hossein(A.S) the grandsons of the Prophet Mohammad (saw), then two young boys, watched him. They immediately realized that the old man was not doing his Wudhu correctly, but hesitated to tell him directly. Perhaps the old man would feel humiliated by two young boys, or he might even lose interest in the act of worship.
Sitting next to him, they started to do the Wudhu and during the Wudhu, Imam Hasan (a.s.) said: "Oh Hussain my Wudhu is correct and more perfect than yours."
In reply, Imam Hussain (a.s.) insisted that his own Wudhu was better than Imam Hasan's.
Finally they said: "Let us refer to this gentleman. He is older than us and should be able to decide."
The old man was listening patiently. The boys performed their Wudhu under his supervision, one after the other. And when they had finished, he realized the Wudhu done by the boys was methodical and correct. It was his own Wudhu which was incorrect. Turning to Imam Hasan (a.s.) and Imam Hussain (a.s.), he gently said: "The Wudhu done by you is correct. I am grateful that you chose to guide me in such a beautiful manner."