Al-ʿAqib and Saiyid, the rulers of Najran, came to Messenger of Allah ﷺ with the intention of doing Lian one of them said to the other, "Do not do (this Lian) for, by Allah, if he is a Prophet and we do this Lian, neither we, nor our offspring after us will be successful." Then both of them said (to the Prophet ﷺ ), "We will give what you should ask but you should send a trustworthy man with us, and do not send any person with us but an honest one." The Prophet ﷺ said, "I will send an honest man who Is really trustworthy." Then every one of the companions of Messenger of Allah ﷺ wished to be that one. Then the Prophet said, "Get up, O Abu 'Ubaida bin Al-Jarrah." When he got up, Messenger of Allah ﷺ said, "This is the Trustworthy man of this (Muslim) nation."  

جَاءَ الْعَاقِبُ وَالسَّيِّدُ صَاحِبَا نَجْرَانَ إِلَى رَسُولِ اللَّهِ ﷺ يُرِيدَانِ أَنْ يُلاَعِنَاهُ قَالَ فَقَالَ أَحَدُهُمَا لِصَاحِبِهِ لاَ تَفْعَلْ فَوَاللَّهِ لَئِنْ كَانَ نَبِيًّا فَلاَعَنَّا لاَ نُفْلِحُ نَحْنُ وَلاَ عَقِبُنَا مِنْ بَعْدِنَا قَالاَ إِنَّا نُعْطِيكَ مَا سَأَلْتَنَا وَابْعَثْ مَعَنَا رَجُلاً أَمِينًا وَلاَ تَبْعَثْ مَعَنَا إِلاَّ أَمِينًا فَقَالَ لأَبْعَثَنَّ مَعَكُمْ رَجُلاً أَمِينًا حَقَّ أَمِينٍ فَاسْتَشْرَفَ لَهُ أَصْحَابُ رَسُولِ اللَّهِ ﷺ فَقَالَ قُمْ يَا أَبَا عُبَيْدَةَ بْنَ الْجَرَّاحِ فَلَمَّا قَامَ قَالَ رَسُولُ اللَّهِ ﷺ هَذَا أَمِينُ هَذِهِ الأُمَّةِ  

The people of Najran came to the Prophet ﷺ and said, "Send an honest man to us." The Prophet ﷺ said, "I will send to you an honest man who is really trustworthy." Everyone of the (Muslim) people hoped to be that one. The Prophet ﷺ then sent Abu Ubaida bin Al-Jarrah.  

جَاءَ أَهْلُ نَجْرَانَ إِلَى النَّبِيِّ ﷺ فَقَالُوا ابْعَثْ لَنَا رَجُلاً أَمِينًا فَقَالَ لأَبْعَثَنَّ إِلَيْكُمْ رَجُلاً أَمِينًا حَقَّ أَمِينٍ فَاسْتَشْرَفَ لَهُ النَّاسُ فَبَعَثَ أَبَا عُبَيْدَةَ بْنَ الْجَرَّاحِ  

The Prophet ﷺ said, "Every nation has an Amin (i.e. the most honest man), and the Amin of this nation is Abu 'Ubaida bin Al-Jarrah."  

عَنِ النَّبِيِّ ﷺ قَالَ لِكُلِّ أُمَّةٍ أَمِينٌ وَأَمِينُ هَذِهِ الأُمَّةِ أَبُو عُبَيْدَةَ بْنُ الْجَرَّاحِ