حَدَّثَنِي عَمْرٌو النَّاقِدُ، حَدَّثَنَا عَفَّانُ، حَدَّثَنَا حَمَّادٌ، - وَهُوَ ابْنُ سَلَمَةَ - عَنْ ثَابِتٍ، عَنْ أَنَسٍ، أَنَّ أَهْلَ الْيَمَنِ، قَدِمُوا عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالُوا ابْعَثْ مَعَنَا رَجُلاً يُعَلِّمْنَا السُّنَّةَ وَالإِسْلاَمَ ‏.‏ قَالَ فَأَخَذَ بِيَدِ أَبِي عُبَيْدَةَ فَقَالَ ‏"‏ هَذَا أَمِينُ هَذِهِ الأُمَّةِ ‏"‏ ‏.‏

Anas reported that the people of Yemen came to Allah's Messenger (PBUH) and said: Send with us a person who should teach us Sunnah and al-Islam, whereupon he (the Holy Prophet) caught hold of the hand of Ubaida and said: He is a man of trust of this Umma. Translation Not Available

Book Ref: Sahih Muslim Book 44 Hadith 5948
Web Ref:  Sahih Muslim Book 31 Hadith 2419 b