It was narrated that 'Uthman bin 'Affan said: "I used to sell dates in the marketplace, and I would say: 'This was such and such an amount (when I bought it).' I would give the purchaser a specific amount of dates according to the way it had been measu.red for me, and take my profit. Then I began to have some doubts about that, so I asked the Messenger of Allah P.B.U.H, and he said: 'When you name the amount, measure it in front of the purchaser.''' (Hasan)