Hadithcore
Sahih al-Bukhari, 2866
sahih

Narrated Anas:

The Prophet (ﷺ) met them (i.e. the people) while he was riding an unsaddled horse with his sword slung over his shoulder.

حَدَّثَنَا عَمْرُو بْنُ عَوْنٍ، حَدَّثَنَا حَمَّادٌ، عَنْ ثَابِتٍ، عَنْ أَنَسٍ ـ رضى الله عنه اسْتَقْبَلَهُمُ النَّبِيُّ صلى الله عليه وسلم عَلَى فَرَسٍ عُرْىٍ، مَا عَلَيْهِ سَرْجٌ، فِي عُنُقِهِ سَيْفٌ‏.‏

References2 variants
In-Book Reference
Book 56, Hadith 82
USC-MSA web (English) reference
Vol. 4, Book 52, Hadith 118 (deprecated numbering scheme)