Amir al-Mu'minin Sayyiduna Umar bin Khattab (may Allah be pleased with him) says: I gave a fine horse in the way of Allah, and the one to whom I gave it ruined it. I thought that now he would sell it for a low price. I asked the Messenger of Allah (peace and blessings of Allah be upon him), and he said: Do not buy it, and do not take back your charity. For the one who takes back his charity is like a dog who vomits and then eats it again.
It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: The one who takes back his gift is like a dog that vomits and then eats its own vomit.