Ijtehaad of Umar regarding names and agnomens

1. It is narrated from Zaid bin Aslam from his father that Umar bin Khattab scolded his son, because his agnomen was Abu Isa. The agnomen of Mughira bin Shoba was also Abu Isa.

Umar said to him: Why did you not give yourself the agnomen of Abu Abdullah? He replied: The Messenger of Allah (s.a.w.a.) kept my agnomen as Abu Isa.

Umar said: The Messenger of Allah (s.a.w.a.) has forgiven past and future sins, but we are responsible for ourselves.  After that he used to address him as Abu Abdullah till he was killed.

[Sonan Abu Dawood, 2:309 [4/291, H. 4963]

2. Wife of Ubaidullah Ibne Umar came to Umar and complained: “O chief of believers, will you not save me from Abu Isa?”

Umar asked: “Who is Abu Isa?”

The wife said: “Your son, Ubaidullah.”

Umar said: “Woe be on you, how can you call him Abu Isa?”

And he summoned his son and asked: “Woe be on you, have you adopted the agnomen of Abu Isa?”

He warned and threatened him; after that he bit his hand till he screamed. Then he beat him up and said: “Woe be on you, did Isa have a father? Can’t you have agnomens, which Arabs adopt? Like Abu Salma, Abu Hanzala, Abu Arfata and Abu Murra.”

[Sharh Nahjul Balagha, 3:104 [12/44, Sermon 223].

3. Umar wrote to the people of Kufa: “Do not name anyone on names of prophets;” and commanded the residents of Medina to change the names of their sons if they were named Muhammad, till some companions of Prophet (s.a.w.a.) said that the Holy Prophet (s.a.w.a.) himself had permitted them to name their sons as Muhammad. At that time he left them alone.

[Umdatul Qari, 7:143 [15/39]