What was the practice of paying in advance for wheat, barley, oil, and dried grapes according to the hadith narrated by Muhammad bin Abi Al-Mujalid (saw) and Ash-Shaibani (peace be upon him)?
 Narrated Muhammad bin Abi Al-Mujalid:                     as above (446) and said, "We used to pay them in advance for wheat and barley (to be delivered later). Narrated Ash-Shaibani--"And also for oil."Narrated Ash-Shaibani:who said "We used to pay in advance for wheat barley and dried grapes."