كتاب المغازى
64  
Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi)
(87)
Chapter: The dispatch of Usama bin Zaid رضي الله عنهما by the Prophet (saws) during his fatal illness
(87)
باب بَعْثُ النَّبِيِّ صلى الله عليه وسلم أُسَامَةَ بْنَ زَيْدٍ ـ رضى الله عنهما ـ فِي مَرَضِهِ الَّذِيتُوُفِّيَ فِيهِ
Sahih al-Bukhari 4468

Narrated Salim's father:

The Prophet (ﷺ) appointed Usama as the commander of the troops (to be sent to Syria). The Muslims spoke about Usama (unfavorably ). The Prophet (ﷺ) 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."

حَدَّثَنَا أَبُو عَاصِمٍ الضَّحَّاكُ بْنُ مَخْلَدٍ، عَنِ الْفُضَيْلِ بْنِ سُلَيْمَانَ، حَدَّثَنَا مُوسَى بْنُ عُقْبَةَ، عَنْ سَالِمٍ، عَنْ أَبِيهِ، اسْتَعْمَلَ النَّبِيُّ صلى الله عليه وسلم أُسَامَةَ ـ فَقَالُوا فِيهِ ـ فَقَالَ النَّبِيُّ صلى الله عليه وسلم ‏ "‏ قَدْ بَلَغَنِي أَنَّكُمْ قُلْتُمْ فِي أُسَامَةَ، وَإِنَّهُ أَحَبُّ النَّاسِ إِلَىَّ ‏"‏‏.‏
Reference : Sahih al-Bukhari 4468
In-book reference : Book 64, Hadith 483
USC-MSA web (English) reference : Vol. 5, Book 59, Hadith 744
  (deprecated numbering scheme)