1612. Ibn `Abbas (May Allah be pleased with them) said: The Messenger of Allah (PBUH) said, "He who gives something (to someone) as a gift and then gets it back (from him or her) is like a dog which eats its own vomit.''

     Another narration is: "He who gets back his charity is like a dog which vomits and then returns to that and eats it.''
[Al-Bukhari and Muslim].

Commentary: The evil and abomination of taking back a gift (Hibah) is evident from the fact that one who does it has been considered akin to a dog, and what is taken back to vomit, which is extremely repulsive. Religious scholars are, however, of the opinion that this injunction is for the strangers (non-relatives). If a person gives something as a gift to his children or grandchildren, this order will not apply to him. It is permissible for him to take it back.

1613. `Umar bin Al-Khattab (May Allah be pleased with him) said: I donated a horse in the way of Allah. Its new possessor did not treat it properly. I made my mind to buy it because I thought that he would sell it at a cheap price (now that it became weak and emaciated). I asked the Prophet (PBUH) about it, whereupon he said, "Do not buy it and do not get back your charity, for one who gets back the charity is like a dog that eats its own vomit.''
[Al-Bukhari and Muslim]

Commentary: We learn from this Hadith that even to purchase something which one has already given in charity is not permissible.