Musnad Ahmad 773:3

Sufyan narrated to us, from Shabib, that he heard the people reporting from Urwah al-Bariqi: "That the Messenger of Allah, peace and blessings of Allah be upon him, sent with him a dinar to buy a sacrificial animal for him," and he said once: "or a sheep." So he bought two for him. Then he sold one for a dinar and brought the other one to him. "So he prayed for blessing for him in his trade," such that if he had bought dust, he would have made a profit on it.