‘Umar b. al-Rhattab said:I provided a man with a horse to ride in God’s path, but as the one who had it did not look after it well, I wanted to buy it and thought he would sell it at a cheap price. I therefore asked the Prophet, but he said,“Do not buy it, and do not take back what you gave as sadaqa even if he gives it to you for a dirham, for the one who takes back what he gave as sadaqa is like a dog which returns to its vomit.”A version has,“Do not take back what you gave as sadaqa, for the one who does so is like one who takes back what he has vomited.”(Bukhari and Muslim.)