Mukhtasar Bukhari (Abridged) 757 — Is it permissible to buy back one's

Amir al-Mu’minin Umar bin Khattab (may Allah be pleased with him) says that (once) I gave a horse in the way of Allah for riding, but the person who had the horse did not value it. I intended to buy it back (because) I thought he would sell it cheaply. Therefore, I asked the Prophet Muhammad (peace be upon him) about this, and he said: “Do not buy it, even if he gives it to you for only one dirham. Indeed, the one who takes back his charity is like the one who eats his own vomit.”