Narrated Abu Humaid As-Saidi: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
Hadith No. 3161
Sahih al Bukhari