Sahih Bukhari Volume 5, Book 57, Hadith Number 77.

Narated By ‘Abdullah bin ‘Umar : The Prophet sent an army under the command of Usama bin Zaid. When some people criticized his leadership, the Prophet said, “If you are criticizing Usama’s leadership, you used to criticize his father’s leadership before. By Allah! He was worthy of leadership and was one of the dearest persons to me, and (now) this (i.e. Usama) is one of the dearest to me after him (i.e. Zaid).”