Abu Dawud
Commercial Transactions
Book Number: 016 / Hadith Number: 3380
Narated By Hakim ibn Hizam : The Apostle of Allah (pbuh) sent with him a dinar to buy a sacrificial animal for him. He bought a sheep for a dinar, sold it for two and then returned and bought a sacrificial animal for a dinar for him and brought the (extra) dinar to the Prophet (pbuh). The Prophet (pbuh) gave it as alms (sadaqah) and invoked blessing on him in his trading.