It is narrated from Sayyiduna Urwah al-Bariqi (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) gave him a dinar so that he could buy a sacrificial goat. He bought two goats with the one dinar, then sold one of them for a dinar, and came to the Prophet (peace and blessings be upon him) with a goat and a dinar. He (peace and blessings be upon him) prayed for blessing for him. After that, even if he bought dust, he would make a profit on it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القراض / 11613