Sahih Bukhari | Volume 5 | 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)