In Islamic commercial law, a sale is valid when the item being sold is sufficiently known and the uncertainty (gharar) is not excessive. The Prophet ﷺ prohibited sales involving gharar fāḥish (excessive uncertainty) because it leads to dispute and injustice (Sahih Muslim). However, scholars have clarified that not every form of uncertainty invalidates a transaction. Minor or customary uncertainty (gharar yasīr) that people normally tolerate is excused.

In this case, the buyer knows several essential elements of the sale: the price is fixed, the seller is known, the item is food, the type of food is generally specified (biryani dishes), and the quantity is approximately understood (a plate of food). The uncertainty lies only in the exact variety of biryani or accompanying items, not in whether the buyer will receive food at all or in its general nature.

Classical jurists permitted similar transactions, such as buying fruit from a basket without selecting each individual piece, or purchasing a house without knowing every detail of its materials, so long as the overall item is known and disputes are unlikely. This type of uncertainty is considered customarily accepted and does not rise to the level of prohibited gharar.

Furthermore, the purpose of the offer is clear: reducing food waste by selling leftover meals at a discounted price. There is no deception, gambling, or zero-sum risk, and the buyer is not exposed to a loss that would normally lead to dispute, since the price is low and the expectation is clearly described.

Therefore, this transaction does not fall under the prohibited category of selling something unknown (bay‘ al-majhūl), and it is permissible, provided that the food itself is halal and the buyer understands and accepts the terms.