What is the ruling on buying an artwork where neither the buyer nor the seller specifies the exact piece beforehand, but rather it is part of a collection of paintings sharing a common theme (e.g., houses), with the buyer knowing they will receive a painting depicting a house but not knowing its precise details before purchasing it, and with no right to return it? Is this considered a sale by sample or a sale of something unknown? And have the Hanafis permitted this type of sale?

For a sale to be valid, knowledge of the item being sold and its price is required, due to the Prophet's (peace be upon him) prohibition of gharar (ambiguous or uncertain transactions), which is anything with an unknown outcome. The majority of scholars hold that the sale of an unknown item is invalid, while a group of Hanafis believe that the sale of an unknown item is valid, even if its type is unknown. As for buying "a painting from among paintings," even if they are similar, it is not valid according to the majority of scholars. This is similar to the sale by sample where the individual units vary; the majority prohibit it, while the Hanafis deem it valid with the option of inspection (khiyar al-ru'yah) for the buyer. The view that it is invalid is more preponderant because seeing a sample does not imply seeing the rest if the individual units vary, thus making the sale of an unknown item, which is impermissible.