The answer is:

This is a story (1) for which he cited no chain of transmission (2). Its authenticity is unknown, and I know of no scholar who has mentioned it. [Had there been any truth to it, they would have mentioned it.] (3) Nor is it known as a report about Umar and Alī; rather, it is well known as a report about Solomon son of David—peace be upon them both. This is authentically established in the two Sahih collections from the Prophet—may Allah bless him and grant him peace—in a hadith narrated by Abū Hurayra, who said:

The Messenger of Allah—may Allah bless him and grant him peace—said: “While two women were together, each with her son, a wolf came and carried off the son of one of them. One of them (4) said to the other, ‘It carried off your son.’ The other said, ‘It carried off your son.’ They brought their dispute before David, who ruled that the child belonged to the older woman. They then went to Solomon son of David and told him what had happened. He said, ‘Bring me a knife, and I will cut him in two between you.’ The younger woman said, ‘Do not do it—may Allah have mercy on you! He is her son.’ So he ruled that the child belonged to the younger woman.”

Abū Hurayra said: “By Allah, I had never heard a knife called a sikkīn until that day; we used to call it only a mudya.” (5).