It is narrated from Aslam (may Allah have mercy on him) that once Sayyiduna Umar (may Allah be pleased with him) gave a horse to someone in the way of Allah for riding. Later, he saw that the same horse was being sold in the market. He thought to himself that he should buy it, so he consulted the Prophet (peace and blessings be upon him). The Prophet (peace and blessings be upon him) forbade him from doing so and said: "Do not buy it, and do not take back what you have given in charity."