Musannaf Ibn Abi Shayba 13:500

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from Layth, from Tawus, and from Abd al-Rahman ibn Amr al-Awza’i, from Ata’, they both said: There is no harm in saying, "This garment is for such-and-such amount in cash, and for such-and-such amount on credit," provided he departs [the transaction] upon one of the two [options].