Musannaf Ibn Abi Shayba 13:35

Abu Sa’d Muhammad ibn Maysar narrated to us, from Ibn Jurayj, from ‘Amr ibn Dinar, from Abu al-Sha’tha’, who said: If one pays in advance for one hundred dinars for one thousand faraq (a unit of measurement), there is no harm if he takes from him five hundred faraq and writes against him fifty dinars.