A man murdered the son of an Ansari. The father of the murdered boy caught hold of the murderer and brought him to Hazrat Omar (RA), who allowed the Ansari to kill the murderer by sword as his son was killed. The Ansari gave two strokes of his sword on the neck of the murderer and thinking him to be dead went away from the scene.
The relations of the murderer who wanted to take his corpse for burial found him still breathing. They took him to some surgeon who succeeded in saving his life with great efforts.
When the Ansari saw him alive , he caught hold of him again and brought him to Hazrat Omar (RA).
Hazrat Omar (RA) ordered for his punishment again till he was dead.
Hazrat Ali (A) asked Hazrat Omar, (RA) “ Had you not ordered for his punishment to death once before ?.”
“Yes”, said Hazrat Omar, (RA) “but as he is still alive, he should be struck with sword again till he is dead.”
Hazrat Ali (A) said to Hazrat Omar (RA): why twice ?
The Ansari who struck him before with his sword twice was satisfied with it and had left him thinking him dead. He was punished as far the punishment under law was concerned. It would be a crime to punish him for the same crime again and again:”
Hazrat Omar (RA) was thinking over what Hazrat Ali (A) had said when the Ansari said to him:
‘Ya Ali! you are allowing the blood of my son to go in vain.
How? enquired Hazrat Ali (A)
“You are allowing the murderer to go away free before I have avenged the murder of my son.”
“Alright.”, said Hazrat Ali (A) let him strike your neck twice with his sword as you struck him before as penalty, then you strike him as many times with your sword as you like till he is dead.”
The Ansari hearing this became afraid of the result, forgave the man involved in the murder of his son and went away.
Thereafter, Hazrat Omar (RA) said to Hazrat Ali (A), All praise is for God ‘O Abul Hasan! you are mercy personified from Ahlul Bait. Had not there been for Al,i Omar would have been ruined.
(Naskihut Tawarikh- Manaqib vol. 00, p I87).