Umar b. Khattab (RA) reported: I donated a pedigree horse in the path of Allah. Its possessor made it languish. I thought that he would sell it at a cheap price. I asked Allah’s Messenger (peace be upon him) about it, whereupon he said: Don’t buy it and do not get back your charity, for one who gets back the charity is like a dog who swallows its vomit.
Sahih Muslim, Book 24, Hadith 1