Tirmidhi

Explanation:
1:
Bay‘ al-Gharar:
It is the sale of something nonexistent or unknown,
or the sale of such a thing over which the seller does not have the ability to deliver it to the buyer.

Benefits and Issues:
(Sale by Pebble) To conduct a sale by throwing a pebble, meaning that the buyer or seller says, "When I throw the pebble, the sale will be finalized," or, "Whatever the pebble lands on, I will give or take that item"—this manner of buying and selling is prohibited. Even today, such a form of gambling is prevalent, where it is said, "Whatever your aim hits will be yours for that price."

(1) Bay‘ al-Hisah: The word "bay‘" is the verbal noun (masdar) of "ba‘a yabī‘u," and "al-hisah" is the plural of "al-hasā." This is not an idafah (construct) of the verbal noun to its object, but rather an idafah of the verbal noun to the type (of sale). Therefore, the meaning of the chapter is: "The sale involving pebbles." There were several forms of this sale, for example: the seller would say to the buyer, "Throw a pebble; whichever garment or other item (that he wished to sell) the pebble lands on, that item will be yours for such-and-such amount." In this, there was neither any right of return, nor the option of majlis (khiyar al-majlis), nor was anything known about any defect or flaw in the garment or other item. Therefore, this sale was in reality a sale of uncertainty (gharar) and deception, which the Shari‘ah has declared unlawful. Another form was that the seller would say to the buyer, "Throw a pebble; wherever it reaches, I will sell you my land up to that point for such-and-such amount." This is a sale of an unknown item, and thus impermissible. There was also the form where the seller would close pebbles in his fist and say, "As many pebbles as come out of my fist, that many items from the goods will be mine." Or he would sell some merchandise and, closing pebbles in his fist, say, "As many pebbles as are in my fist, I will take that many dirhams or dinars," i.e., whatever was agreed upon. Sometimes, they would do it in such a way that one of the parties to the transaction would take pebbles in his hand and say, "Whenever the pebbles fall, the sale will become binding." Sometimes, they would make the throwing of the pebble itself the cause for the sale to become binding. All these statements have been mentioned by Imam Nawawi and Imam Abu al-‘Abbas al-Qurtubi rahimahullah (Sharh Sahih Muslim, al-Buyu‘, Bab Butlan Bay‘ al-Hisah wa al-Bay‘ alladhi fihi al-Gharar: 10/220).

(2) At the end of the hadith, every sale involving deception has been prohibited, for example: the sale of a fish present in water or a bird flying in the air which has not yet been hunted. Allah knows whether it will be caught or not. Similarly, the sale of a runaway slave—who knows whether he will be found or not. The sale of something that has not yet come into existence also falls under this, and so on. However, if there is a little ambiguity which cannot be avoided, then there is allowance for it, for example: renting something on a monthly or daily basis, even though not all months or all days are equal—there is variation in them. But this is a necessity, so it is permissible without difficulty. Moreover, there is no concept of deception in these, which is the real basis for the prohibition.