Sahih Bukhari Volume 008, Book 078, Hadith Number 623.
Narated By Ibn 'Umar : Allah's Apostle sent an army detachment and made Usama bin Zaid its commander. Some people criticized (spoke badly of) Usama's leadership. So Allah's Apostle got up saying, "If you people are criticizing Usama's leadership, you have already criticized the leadership of his father before. But Wa-aimullah (i.e., By Allah), he (i.e. Zaid) deserved the leadership, and he was one of the most beloved persons to me; and now this (his son Usama) is one of the dearest persons to me after him." (See Hadith No. 745, Vol. 5)