Musnad Ahmad 281

‘Abd al-Rahman narrated to us, from Malik, from Zayd ibn Aslam, from his father, from ‘Umar ibn al-Khattab, may Allah be pleased with him, who said: ‘I supplied a horse for Allah’s cause, but the man to whom I gave it neglected it. I wanted to buy it, thinking he would sell it cheaply, but I said, “I should ask the Messenger of Allah, peace and blessings be upon him.” He said, “Do not buy it, even if he gives it to you for a dirham. The one who takes back his charity is like a dog returning to its vomit.”’