Sahih Bukhari Volume 4, Book 58, Hadith 3161

فَقَالَ النُّعْمَانُ رُبَّمَا أَشْهَدَكَ اللَّهُ مِثْلَهَا مَعَ النَّبِيِّ صلى الله عليه وسلم فَلَمْ يُنَدِّمْكَ وَلَمْ يُخْزِكَ، وَلَكِنِّي شَهِدْتُ الْقِتَالَ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا لَمْ يُقَاتِلْ فِي أَوَّلِ النَّهَارِ انْتَظَرَ حَتَّى تَهُبَّ الأَرْوَاحُ وَتَحْضُرَ الصَّلَوَاتُ‏

Narrated By Abu Humaid As-Saidi : We accompanied the Prophet 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 wrote to him a peace treaty allowing him to keep authority over his country.