It is narrated from Hazrat Abu Sa'id Khudri (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: Gold for gold, silver for silver, wheat for wheat, barley for barley, dates for dates, and salt for salt should be exchanged equally. Whoever adds to it or demands an addition, he engages in usury, and in this both the taker and the giver are equal.