Musannaf Ibn Abi Shayba 13:452

Abu Bakr narrated to us, he said: Abu Mu'awiyah narrated to us, from Abd al-Rahman ibn 'Ajlan, he said: I said to Ibrahim: "We buy goods, then we add to them the cost of bleaching and the transport fee, then we sell them for a dinar of profit." He said: "There is no harm in that."