Sahih Bukhari
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
Volume: 005 / Book Number: 059 / Hadith Number: 744
Narrated Salim's father:
The Prophet appointed Usama as the commander of the troops (to be sent to Syria). The Muslims spoke about Usama (unfavorably ). The Prophet said, " I have been informed that you spoke about Usama. (Let it be known that ) he is the most beloved of all people to me."