Yahya related to me from Malik from Humayd ibn Qays al-Makki thatMujahid said, "I was with Abdullah ibn Umar and an artisan came to himand said, 'Abu Abd ar-Rahman - I fashion gold and then sell what Ihave made for more than its weight. I take an amount equivalent to thework of my hand.' Abdullah forbade him to do that, so the artisanrepeated the question to him, and Abdullah continued to forbid himuntil he came to the door of the mosque or to an animal that heintended to mount. Then Abdullah ibn Umar said, 'A dinar for a dinar,and a dirham for a dirham. There is no increase between them. This isthe command of ourProphet to us and our advice to you.' "
USC-MSA web (English) reference: Book 31, Hadith 31
Arabic reference: Book 31, Hadith 1322