Islamic banking: some ideas

Principle: the lender must share in the profits or losses arising out of the enterprise for which the money was lent.

"Islam encourages Muslims to invest their money and to become partners in order to share profits and risks in the business instead of becoming creditors. As defined in the Shari'ah, or Islamic law, Islamic finance is based on the belief that the provider of capital and the user of capital should equally share the risk of business ventures, whether those are industries, farms, service companies or simple trade deals. Translated into banking terms, the depositor, the bank and the borrower should all share the risks and the rewards of financing business ventures. This is unlike the interest-based commercial banking system, where all the pressure is on the borrower: he must pay back his loan, with the agreed interest, regardless of the success or failure of his venture. The principle which thereby emerges is that Islam encourages investments in order that the community may benefit"

From this website.