2 The rule concerning uncertainty (gharar) and ignorance (jahālah).
3 The rule concerning fraud and deception.

These three principles are the foundation of all forbidden transactions. Under them fall a host of particular forms and details—contracts and rulings that Islam declares unlawful. The Sharia has spelled out the laws of commercial dealings, personal status, criminal offenses, and penalties, which shows that Islam is both religion and state: just as it is concerned with the acts of worship that bind a servant to his Lord, it likewise regulates his actions and conduct in the affairs of worldly life.

Indeed, Islam has not left anything that would set this society aright without organizing it in the finest manner: “Who could give better judgment than Allah for a people who are certain in faith?” (Q 5:50).

The conditions of sale and the matters forbidden therein

Conditions (shurūt, sing. shart) are defined as factors whose absence entails the non-existence of the act they govern, while their presence does not, in and of itself, necessitate either its existence or non-existence.

A sale is a contract whose validity depends on the fulfillment of its conditions and the removal of its impediments; without that it cannot be deemed a valid agreement.

From the jurists’ investigation and analysis, the conditions for a valid sale may be summarized as follows:

1 Mutual consent of the contracting parties: a sale concluded under unjust duress is invalid. Shaykh ʿAbd al-Rahman ibn Saʿdi said, “Consent is an established principle drawn from the Qur’an, the Sunnah, and scholarly consensus, and it is required by justice and fairness.”

2 Legal capacity of the parties—the seller and the buyer—so that each is competent to dispose of property, being a discerning and accountable person.

3 The subject matter—or its usufruct, whether the price or the commodity—must be something whose benefit is lawful.

4 The contractor must either own the subject matter or be duly authorized to contract over it.