Shaykh ʿAbd al-Rahman ibn Saʿdi added, “This rule stands solidly on the Qur’an, the Sunnah, unanimous agreement, and analogical reasoning.”
5 – The subject matter of the contract must be deliverable.
6 – Both the commodity and the price have to be known to seller and buyer; a sale involving the unknown is invalid.

Anything the Sharia forbids in sales stems either from ignorance (jahalah), from excessive uncertainty (gharar), or from one of the various forms of usury (riba). The details of these prohibitions will follow, God willing.

Resolution of the Fiqh Council on the ruling for concluding contracts through modern means of communication

In the name of Allah, the Most Gracious, the Most Merciful.

All praise belongs to Allah, Lord of the worlds; and may blessings and peace be upon our master Muhammad, the Seal of the Prophets, and upon his family and companions.

The Council of the Islamic Fiqh Academy, convened for its sixth session in Jeddah, Kingdom of Saudi Arabia, from 17 to 23 Shaʿban 1410 AH (14–20 March 1990 CE), after reviewing the papers submitted to the Academy on the topic “Concluding contracts through modern means of communication,” and in view of the great advances in communication technology and its widespread use for swift completion of financial transactions and dispositions, and mindful of the jurists’ discussions on contracting by spoken word, by written text, by gesture, and by messenger, as well as the established rule that when the parties are physically present a single session is required—except in bequests, mandates, and agency—together with the conditions of correspondence between offer and acceptance, the absence of any indication that either party has withdrawn, and the customary proximity between offer and acceptance