We accompanied the Prophet ﷺ in the Ghazwa of Tabuk and the king of 'Aila presented a white mule and a cloak as a gift to the Prophet. And the Prophet ﷺ wrote to him a peace treaty allowing him to keep authority over his country.  

غَزَوْنَا مَعَ النَّبِيِّ ﷺ تَبُوكَ وَأَهْدَى مَلِكُ أَيْلَةَ لِلنَّبِيِّ ﷺ بَغْلَةً بَيْضَاءَ وَكَسَاهُ بُرْدًا وَكَتَبَ لَهُ بِبَحْرِهِمْ