(137) باب إِذَا حَمَلَ عَلَى فَرَسٍ فَرَآهَا تُبَاعُ
Narrated `Abdullah bin `Umar:
`Umar bin Al-Khattab gave a horse to be ridden in Allah's Cause and then he found it being sold. He intended to purchase it. So, he consulted Allah's Messenger (ﷺ) who said, "Don't buy it and don't take back your gift of charity."
Reference: Sahih al-Bukhari 3002
In-book reference: Book 56, Hadith 211
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 4, Book 52, Hadith 246