Amr bin Harish (may Allah have mercy on him) says that I asked Sayyiduna Ibn Amr (may Allah be pleased with him) that we are in a place where dinar or dirham are not in use, so we buy and sell camels and goats for a fixed period. What is your opinion about this? He replied: "You have asked a knowledgeable man. Once, the Prophet Muhammad (peace and blessings be upon him) prepared an army in the hope that the camels of charity would arrive. The camels ran out and some people were left (who could not get mounts). The Prophet (peace and blessings be upon him) said to me: 'Buy camels for us on the condition that when the camels of charity arrive, they will be given in their place.' So I bought one camel in exchange for two camels, and sometimes in exchange for three, until I was done, and the Prophet (peace and blessings be upon him) paid them from the camels of charity."