(100) باب شِرَاءِ الصَّدَقَةِ
It was narrated from 'Umar that:
he gave someone a horse to ride in the cause of Allah, then he saw it offered for sale and wanted to buy it. The Prophet said to him: "Do not think of buying back what you have given in charity."
Reference: Sunan an-Nasa'i 2616
In-book reference: Book 23, Hadith 0
English translation: Vol. 3, Book 23, Hadith 2617