Musnad Ahmad 1034:136

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, he said: I heard Abu Ishaq narrating from Silah ibn Zufar, from Hudhayfah, that he said: The people of Najran came to the Messenger of Allah, may Allah bless him and grant him peace, and said: "Send with us a trustworthy man." He said: "I will surely send to you a trustworthy man, truly trustworthy, truly trustworthy." He said: So the people craned their necks for it [hoping to be chosen]. He said: Then he sent Abu Ubaydah ibn al-Jarrah.