The people of Najran came to the Prophet (ﷺ) and said, "Send an honest man to us." The Prophet (ﷺ) said, "I will send to you an honest man who is really trustworthy." Everyone of the (Muslim) people hoped to be that one. The Prophet (ﷺ) then sent Abu Ubaida bin Al-Jarrah.
Sahih al-Bukhari Book 64, Hadith 404
← Previous Hadith Al-`Aqib and Saiyid, the rulers of Najran, came to Allah's Messenger (ﷺ) with the intention of doing Lian one of them said to the other, "Do not do (this Lian) for, by Allah, if he is a Prophet and we do this Lian, neither we, nor our offspring after us will be successful." Then both of them said (to the Prophet (ﷺ) ), "We will give what you should ask but you should send a trustworthy man with us, and do not send any person with us but an honest one." The Prophet (ﷺ) said, "I will send an honest man who Is really trustworthy." Then every one of the companions of Allah's Messenger (ﷺ) wished to be that one. Then the Prophet said, "Get up, O Abu 'Ubaida bin Al-Jarrah." When he got up, Allah's Messenger (ﷺ) said, "This is the Trustworthy man of this (Muslim) nation."

Sahih al-Bukhari Book 64, Hadith 403 Next Hadith → The Prophet (ﷺ) said, "Every nation has an Amin (i.e. the most honest man), and the Amin of this nation is Abu 'Ubaida bin Al-Jarrah."

Sahih al-Bukhari Book 64, Hadith 405