What is the ruling on selling 100 sheep from a flock of 300 sheep without specifying them, on the condition that the buyer chooses them after the sale is complete?

The issue of the validity of selling an unspecified sheep from a flock is summarized in several opinions: The sale is voidable (fasid) except for a few, with the option of designation for the buyer (Hanafis and one opinion among Hanbalis); or it is absolutely void (batil) (Shafi'is and Hanbalis); or it is valid for both a few and many, provided there is an option of designation (Imam Malik); or it is valid if the values are equal (Abu Ja'far and Abu al-Khattab from the Hanbalis). Ibn 'Uthaymin inclined towards permissibility if the values are close and there is no significant ignorance (jahalah) or gharar (deception/risk), based on custom and the principle that the original ruling for transactions is permissibility and validity.