It is narrated from Sayyiduna Umar bin Khattab (may Allah be pleased with him) that he saw a horse for sale in the market which he himself had given in charity. So Sayyiduna Umar (may Allah be pleased with him) asked the Messenger of Allah (peace and blessings be upon him), "Can I buy it?" The Prophet (peace and blessings be upon him) said: "Do not buy it, nor buy anything from it in the future."
Hadith Referenceالسنن المأثورة / باب ما جاء في صدقة الفطر / 370
Hadith Takhrijصحیح بخاری، الجہاد والسیر، باب الجعائل والحملان فی السبیل، رقم : 1490,2970 ، صحیح مسلم، الہبات، باب کراہۃ شراء الانسان ما تصدق بد ممن تصدق علیہ، رقم : 1620