Furthermore, legal transactions fall into two categories: contracts and acts of taking possession. The Prophet, may Allah bless him and grant him peace, brought both together in his words:

“May Allah have mercy on a servant who is gracious when selling, gracious when buying, gracious when paying what he owes, and gracious when claiming what is owed to him.”

People likewise speak of buying and selling, taking and giving.

The purpose of contracts is simply to take possession and receive what is due. Concluding a contract makes taking possession obligatory or permissible, in a manner analogous to the Lawgiver’s imposition of obligations. The subsequent exchange of possession and similar acts fulfil contracts, just as performing what is commanded fulfils religious obligations. Taking possession, like a contract, may be valid or invalid, and legal rulings attach to it, just as they attach to taking possession.

If taking possession is determined by people’s customs and practices, without a single definition applying equally to everyone in every circumstance and at every time, then the same applies to contracts. If you formulate the argument more precisely, you would say: Contracts constitute one of the two categories of legal transactions; their determination therefore rests on people’s customary practice, just as it does for the other category.

A related point is that permission conveyed through customary practice—whether to allow use, transfer ownership, or authorize action through agency—is equivalent to verbal permission. Both agency and permission to use something are established by words or actions indicating them. Knowing that the person entitled to grant permission consents takes the place of that person’s express declaration of consent. This also explains the pledge of allegiance given by the Prophet