Sahih Bukhari Volume 005, Book 059, Hadith Number 552.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 59. Military Expeditions Led by the Prophet (PBUH) (Al-Maghaazi)
Narrated By Ibn Umar : Allah's Apostle appointed Usama bin Zaid as the commander of some people. Those people criticized his leadership. The Prophet said, "If you speak ill of his leadership, you have already spoken ill of his father's leadership before. By Allah, he deserved to be a Commander, and he was one of the most beloved persons to me and now this (i.e. Usama) is one of the most beloved persons to me after him.