´Narrated Anas bin Malik:` that the Messenger of Allah (ﷺ) said: "The most merciful of my nation to my nation is Abu Bakr, and the most severe of them concerning the order of Allah is 'Umar, and the most truly modest of them is 'Uthman bin 'Affan. The best reciter (of the Qur'an) among them is Ubayy bin Ka'b, the most knowledgeable of them concerning (the laws of) inheritance is Zaid bin Thabit, the most knowledgeable of them concerning the lawful and the unlawful is Mu'adh bin Jabal. Truly, every nation has a trustworthy one, and the trustworthy one of this nation is Abu 'Ubaidah bin Al-Jarrah."
Hadith Referenceسنن ترمذي / كتاب المناقب عن رسول الله صلى الله عليه وسلم / 3791
´Narrated Anas bin Malik:` that the Messenger of Allah (ﷺ) said: "The most merciful of my nation to my nation is Abu Bakr, and the most severe of them concerning the order of Allah is 'Umar, and the most truly modest of them is 'Uthman bin 'Affan. The most knowledgeable of them concerning the lawful and unlawful is Mu'adh Bin Jabal, the most knowledgeable of them concerning (the laws of) inheritance is Zaid bin Thabit, the best reciter (of the Qur'an) among them is Ubayy bin Ka'b, and every nation has a trustworthy one, and the trustworthy one of this nation is Abu 'Ubaidah Bin Al-Jarrah."
Shaykh Dr. Abdur Rahman Freywai
Explanation: 1: Although all the Companions were trustworthy (amin), Abu Ubaydah radi Allahu anhu was distinguished in this regard. Therefore, he was given the title (Amin al-Ummah) (in today's terminology, the General Secretary of the entire Ummah). In the same way, many good qualities are shared by many Companions, but some have a particular characteristic due to which the Prophet sallallahu alayhi wa sallam declared them distinguished in that quality. For example, in modesty (haya), ‘Uthman; in judicial matters (qada’), ‘Ali; in inheritance (mirath), Zayd ibn Thabit; and in recitation (qira’ah), Ubayy ibn Ka‘b, and others radi Allahu anhum. (See the next hadith)
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 3790
Narrated Abu Qilabah on the authority of Anas (RA): Allah's Messenger (ﷺ) said: "The most versed in the rules of inheritance among you is Zaid bin Thabit." [Reported by Ahmad and al-Arba'a except Abu Dawud. at-Tirmidhi, Ibn Hibban and al-Hakim graded it Sahih (authentic). However, it was considered defective due to being Mursal (missing link in the chain after the Tabi'i)].