Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.078A.

The Messenger of Allah, upon whom be peace, prohibited the one who gives zakah to buy back what he gave up for Allah, the Exalted One. This is similar to the case of those immigrants who were prohibited (by the Messenger) to return to Makkah after they had left it as immigrants. It is related by ‘Abdullah ibn ‘Umar that: “Once ‘Umar gave away a horse, for the cause of Allah, as sadaqah. Later, he saw it for sale and wanted to buy it. He asked the Messenger of Allah, upon whom be peace, if he could do so. The Messenger answered: ‘Do not buy back what you gave in sadaqah.'” This is related by al-Bukhari, Muslim, Abu Dawud, and an-Nasa’i. AnNawawi says it is a purifying prohibition, not one of unlawfulness. It is unsuitable (makruh) for a person to buy back what he has given in sadaqah, or zakah, or penance for a promise, or anything of the nature which brings one closer to Allah, the Exalted One. This is also applicable to a gift offered to someone which the donor cannot own even if it is allowed by the recipient. However, it can be owned by him again if he inherits it. According to Ibn Battal, most scholars disliked someone to buy his sadaqah back. This is in accordance with ‘Umar’s hadith. Ibn al-Munzhir says that al-Hasan, ‘Ikrimah, Rabi’ah, and al-Auza’i allowed buying one’s charity back. Ibn Hazm is also inclined to this view because of a hadith from Abu Sa’id alKhudri. The Messenger of Allah, upon whom be peace, said: “Sadaqah is not allowed to the well-to-do except for five among them: one who fights in the cause of Allah; one who administers zakah; one who is in debt; one who bought [the article of zakah] with his money; or one who has a poor neighbour to whom he gave sadaqah, and the latter gave it as a gift to him.”