It reached Imam Malik, may Allah have mercy on him, that a man wanted to buy grain from another man on a promise, so the seller took the buyer to the market and, showing him the sacks, said: Which grain shall I buy for you? The buyer said: Do you sell to me something which you do not possess yourself? Then both the seller and the buyer went to Sayyiduna Abdullah bin Umar, may Allah be pleased with them both, and informed him of this. Sayyiduna Abdullah bin Umar, may Allah be pleased with them both, said to the buyer: Do not buy that which the seller does not possess, and to the seller he said: Do not sell that which you do not possess.