Hadithcore
Sahih al-Bukhari, 4468
sahih

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 ‏

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References2 variants
In-Book Reference
Book 64, Hadith 483
USC-MSA web (English) reference
Vol. 5, Book 59, Hadith 744 (deprecated numbering scheme)