I gave a horse to be used in Allah's Cause, but later on I saw it being sold. I asked the Prophet (ﷺ) whether I could buy it. He said, "Don't buy it and don't take back your gift of charity."
Sahih al-Bukhari Book 56, Hadith 179
← Previous Hadith Once the people got frightened, so Allah's Messenger (ﷺ) rode a slow horse belonging to Abu Talha, and he set out all alone, making the horse gallop. Then the people rode, making their horses gallop after him. On his return he said, "Don't be afraid (there is nothing to be afraid of) (and I have found) this horse a very fast one." That horse was never excelled in running hence forward. (Qastalani Vol. 5)

Sahih al-Bukhari Book 56, Hadith 178 Next Hadith → `Umar gave a horse to be used in Allah's Cause, but later on he found it being sold. So, he intended to buy it and asked Allah's Messenger (ﷺ) who said, "Don't buy it and don't take back your gift of charity."

Sahih al-Bukhari Book 56, Hadith 180