Anas reported that the people of Yemen came to Allah's Messenger (ﷺ) 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.
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 " .
Muslim
The Book of the Merits of the Companions • Hadith 83