The people of Najran came to the Prophet ﷺ and said, "Send us a trustworthy man."He replied, "I will send to you a man who is truly trustworthy, genuinely trustworthy."The people eagerly looked forward to being chosen, and he sent Abu Ubayda bin al-Jarrah.
جاء أهل نجران إلى النبي ﷺ فقالوا: ابعث لنا رجلا أمينا فقال: لأبعثن إليكم رجلا أمينا حق أمين فاستشرف له الناس، فبعث أبا عبيدة بن الجراح.
Bukhari related it in the Book of Military Expeditions (4381), and Muslim related it in the Book of the Virtues of the Companions (2420-55), both from Muhammad bin Bashshar, who said, Muhammad bin Jafar narrated to us, Shuba narrated to us, he said, I heard Abu Ishaq narrate from Salah bin Zafar, from Huzaifa, and he mentioned it. In another wording, from a different route, in Bukhari (4380),"The Aqib and the Sayyid, the two leading men of Najran, came to the Messenger of Allah ﷺ wanting to challenge him to a mutual imprecation. One of them said to his companion, 'Do not do it. By Allah, if he is truly a prophet and we invoke this against him, we will not prosper, neither we nor our descendants after us.' They said, 'We will give you what you have asked of us, so send with us a trustworthy man, and send with us none but a trustworthy man.' He said, 'I will indeed send with you a trustworthy man, truly trustworthy.' The companions of the Messenger of Allah ﷺ each hoped to be chosen for it, but he said, 'Stand up, Abu Ubayda bin Jarrah.' When he stood up, the Messenger of Allah ﷺ said, 'This is the trustworthy one of this nation.'"