(119) باب الْجَعَائِلِ وَالْحُمْلاَنِ فِي السَّبِيلِ
Narrated `Umar bin Al-Khattab:
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."
Reference: Sahih al-Bukhari 2970
In-book reference: Book 56, Hadith 179
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 4, Book 52, Hadith 214