Sayyiduna Ziyad bin al-Harith al-Suda'i (may Allah be pleased with him) says: I was with the Prophet (peace and blessings be upon him) on a journey. When the time of the Fajr prayer came, he (peace and blessings be upon him) said to me: "O brother of Suda', give the adhan." So I gave the adhan while on my mount.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 5268