Musannaf Ibn Abi Shayba 13:1070

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Ibn Jurayj, from ‘Ata’, that Ibn al-Zubayr used to give the merchants money here and take [the equivalent] from them in another land. So I mentioned it, or it was mentioned to Ibn ‘Abbas, and he said: "There is no harm in it, as long as he does not stipulate [a condition]."