Sahih Bukhari Volume 5, Book 59, Hadith Number 664.

Narrated By Hudhaifa : The people of Najran came to the Prophet and said, “Send an honest man to us.” The Prophet 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 then sent Abu Ubaida bin Al-Jarrah.