(2) باب إِذَا وَادَعَ الإِمَامُ مَلِكَ الْقَرْيَةِ هَلْ يَكُونُ ذَلِكَ لِبَقِيَّتِهِمْ
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.
Reference: Sahih al-Bukhari 3161
In-book reference: Book 58, Hadith 4
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 4, Book 53, Hadith 387