Umar gave a horse of his to be used in the cause of Allah, handing it over to the Messenger of Allah ﷺ so that it could be given to a man to ride. Later, Umar was told that the man had put it up for sale, so he asked the Messenger of Allah ﷺ whether he could buy it back.He replied, "Do not buy it, and do not take back what you have given in charity."
حدثنا مسدد حدثنا يحيى حدثنا عبيد الله قال حدثني نافع
أن عمر حمل على فرس له في سبيل الله أعطاها رسول الله ﷺ ليحمل عليها رجلا فأخبر عمر أنه قد وقفها يبيعها فسأل رسول الله ﷺ أن يبتاعها فقال لا تبتعها ولا ترجعن في صدقتك