Sahih Bukhari Volume 5, Book 59, Hadith Number 396.

Narrated By Al-Bara’ bin ‘Azib: The Prophet appointed Abdullah bin Jubair as the commander of the cavalry archers on the day of the battle of Uhud. Then they returned defeated, and that what is referred to by Allah’s Statement: “And the Apostle (Muhammad) in your rear was calling you.” (3.153)