Sahih al-Bukhari 2636
صحيح البخاري#2636SahihNarrated `Umar bin Al-Khattab:Once I gave a horse (for riding) in Allah's Cause. Later I saw it being sold. I asked Allah's Messenger (ﷺ) (whether I could buy it). He said, "Don't buy it, for you should not get back what you have given in charity
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih al-Bukhari is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 51:68