It was narrated that Abu Laila Al-Kindi said: Khabbab came to `Umar and said: 'Come close, for no one deserves this meeting more than you, except `Ammar.' Then Khabbab started to show him the marks on his back where the idolaters had tortured him.
It was narrated from Anas bin Malik that: The Messenger of Allah said: The most merciful of my Ummah towards my Ummah is Abu Bakr; the one who adheres most sternly to the religion of Allah is 'Umar; the most sincere of them in shyness and modesty is 'Uthman; the best judge is 'Ali bin Abu Talib; the best in reciting the Book of Allah is Ubayy bin Ka'b; the most knowledgeable of what is lawful and unlawful is Mu'adh bin Jabal; and the most knowledgeable of the rules of inheritance (Fara'id) is Zaid bin Thabit. And every nation has a trustworthy guardian, and the trustworthy guardian of this Ummah is Abu 'Ubaidah bin Jarrah.
Another chain with similar wording (as no. 154) but he said that: Zaid was: The most knowledgeable of them concerning the rules of inheritance.