Is it permissible to subscribe to a service that sends the subscriber a monthly box containing samples or full-sized packages of various cosmetic products, the contents of which are not known beforehand, even though the subscriber is aware of the companies contracted with this service, and does this fall under the prohibited gharar (uncertainty)?

For a sale to be valid, both the buyer and the seller must have knowledge of the commodity being sold, due to the Prophet's (peace be upon him) prohibition of gharar (uncertainty) sales, which refers to anything involving an unknown item. Examples of this include: bay' al-mulamasah (touching sale), bay' al-munabadhah (throwing sale), bay' al-hasah (pebble sale), buying a box containing an unknown item, and selling sealed boxes whose contents are unknown. These sales are forbidden because of the gharar they contain, which leads to animosity and hatred.