‘Amr b. Shu'aib, on his father’s authority, said his grandfather told that God’s Messenger forbade the type of transaction in which earnest money was paid (An arrangement by which the earnest-money was treated as part of the price if the deal was completed but was retained if it was not completed).
Anas said that a man of Kilab asked the Prophet about hiring a stallion to cover a female and he forbade him; but when he said, "Messenger of God, we lend a stallion to cover a female and are given a present," he gave him licence to accept a present.
Ibn ‘Umar said the Prophet forbade selling a debt to be paid at a future date for another (This is allowing a man who cannot pay a debt when it is due to have an extension of the period in return for an additional sum payable; or when a man agrees to sell an article which someone owes him for money which someone else owes to the buyer.
