Rule-1: The subject of sale must be existing at the time of
sale.
Thus, a thing which has not yet come into existence cannot
be sold. If a non-existent thing has been sold, though by
mutual consent, the sale is void according to Shari‘ah.
Example: A sells the unborn calf of his cow to B. The sale is
void.
Rule-2: The subject of sale must be in the ownership of the
seller at the time of sale.
Thus, what is not owned by the seller cannot be sold. If
he sells something before acquiring its ownership, the sale is
void.
Example: A sells to B a car which is presently owned by C,
but A is hopeful that he will buy it from C and shall deliver
it to B subsequently. The sale is void, because the car was
not owned by A at the time of sale.
Rule-3: The subject of sale must be in the physical or
constructive possession of the seller when he sells it to
another person.
"Constructive possession" means a situation where the
possessor has not taken the physical delivery of the
commodity, yet the commodity has come into his control, and
all the rights and liabilities of the commodity are passed on
to him, including the risk of its destruction.
Examples :
(i) A has purchased a car from B. B has not yet delivered it
to A or to his agent. A cannot sell the car to C. If he sells
it before taking its delivery from B, the sale is void.
(ii) A has purchased a car from B. B, after identifying the
Car has placed it in a garage to which A has free access and B
has allowed him to take the delivery from that place whenever
he wishes. Thus the risk of the Car has passed on to A.. The
car is in the constructive possession of A. If A sells the car
to C without acquiring physical possession, the sale is valid.
Explanation 1:
The gist of the rules mentioned in paragraphs 1 to 3 is that a
person cannot sell a commodity unless:
(a) It has come into existence.
(b) It is owned by the seller.
(c) It is in the physical or constructive possession of the
seller.
Explanation 2:
There is a big difference between an actual sale and a mere
promise to sell. The actual sale cannot be effected unless the
above three conditions are fulfilled. However one can promise
to sell something which is not yet owned or possessed by him.
This promise initially creates only a moral obligation on the
promisor to fulfil his promise, which is normally not
justifiable. Nevertheless, in certain situations, specially
where such promise has burdened the promise with some
liability, it can be enforceable through the courts of law. In
such cases the court may force the promisor to fulfil his
promise, i.e. to effect the sale, and if he fails to do so,
the court may order him to pay the promise the actual damages
he has incurred due to the default of the promisor.
But the actual sale will have to be effected after the
commodity comes into the possession of the seller. This will
require separate offer and acceptance, and unless the sale is
effected in this manner, the legal consequences of the sale
shall not follow.
Exception:
The rules mentioned in paragraphs 1 to 3 are relaxed with
respect to two types of sale, namely:
(a) Bai‘ Salam
(b) Istisna’
Rule-4: The sale must be instant and absolute. Thus a sale
attributed to a future date or a sale contingent on a future
event is void. If the parties wish to effect a valid sale,
they will have to effect it afresh when the future date comes
or the contingency actually occurs.
Examples:
(a) A says to B on the first of January: "I sell my car to you
on the first of February". The sale is void, because it is
attributed to a future date.
(b) A says to B, "If party X wins the elections, my car stands
sold to you". The sale is void, because it is contingent on a
future event.
Rule-5: The subject of sale must be a property of value.
Thus, a thing having no value according to the usage of trade
cannot be sold or purchased.
Rule-6: The subject of sale should not be a thing which is
not used except for a haram purpose, like pork, wine etc.
Rule-7: The subject of sale must be specifically known and
identified to the buyer.
Explanation:
The subject of sale may be identified either by pointation or
by detailed specification which can distinguish it from other
things not sold.
Example:
There is a building comprising a number of apartments built in
the same pattern. A, the owner of the building says to B, "I
sell one of these apartments to you"; B accepts. The sale is
void unless the apartment intended to be sold is specifically
identified or pointed out to the buyer.
Rule-8: The delivery of the sold commodity to the buyer
must be certain and should not depend on a contingency or
chance.
Example : A sells his car stolen by some anonymous
person and the buyer purchases it under the hope that he will
manage to take it back. The sale is void.
Rule-9: The certainty of price is a necessary condition for
the validity of a sale. If the price is uncertain, the sale is
void.
Example: A says to B, "If you pay within a month, the
price is Rs. 50. But if you pay after two months, the price is
Rs. 55". B agrees. The price is uncertain and the sale is
void, unless anyone of the two alternatives is agreed upon by
the parties at the time of sale.
Rule-10: The sale must be unconditional. A conditional sale
is invalid, unless the condition is recognized as a part of
the transaction according to the usage of trade.
Example:
(i) A buys a car from B with a condition that B will employ
his son in his firm. The sale is conditional, hence invalid.
(ii) A buys a refrigerator from B, with a condition that B
undertakes its free service for 2 years. The condition, being
recognized as a part of the transaction, is valid and the sale
is lawful.