What is an interest-free loan (Qard Hasan), and what are its conditions and rulings?

A loan is the act of giving money to be used by the borrower, who then repays its equivalent. Its purpose is to assist those in need. As for a "goodly loan" (Qard Hasan (definition)), it is given with a sincere intention and a willing heart, seeking only the Countenance of Allah without any obligation or harm. It is preferable that it be from lawful wealth. The wise Sharia (definition) has encouraged it, for its reward is immense, as Allah Almighty says: "Who is it that would loan Allah a goodly loan so He may multiply it for him many times over?" And as the Prophet, peace and blessings be upon him, said: "A loan is eighteenfold [in reward]," because the borrower only seeks it out of necessity. In some aspects, it is better than charity. A condition for a goodly loan is that the lender must not stipulate any increase or benefit in return for the loan.