Narrated Hudhaifah bin Al-Yaman:that Al-'Aqib and As-Sayyid (two of the leaders of the Christians of Najran) came to the Prophet (ﷺ) and said: "Send with us your trustworthy one." He said: "I shall send with you a trustworthy one who is truly a trustworthy one." So the people desired that, and he sent Abu 'Ubaidah, may Allah be pleased with him

English translation · Jami' at-Tirmidhi