Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated from the Messenger of Allah (peace and blessings be upon him), he (peace be upon him) said: "Whoever buys grain should not sell it until he measures it." I said to Sayyiduna Ibn Abbas (may Allah be pleased with them both): Why? He said: Do you not see that they used to sell it for gold coins while there was only hope of the grain arriving?