What is the ruling on a merchant selling black honey and tahini in pre-weighed containers without ensuring the buyer is aware of the weight, and does this fall under the category of "bay' al-juzaf" (sale by estimation) which is prohibited by Sharia?

If the weight of the dish is written on it, this is not considered a sale of the unknown (gharaar) or a bulk sale (juzāf), and the fact that the buyer cannot read does not alter the ruling. The buyer can inquire about the weight. This is particularly true in our era, where the custom of writing the weight of goods for sale has become widespread.

Selling by bulk (juzāf) is permissible by consensus (ijmā‘) due to people's need for it, despite the presence of some ignorance (jahālah) in it. The Malikis have detailed the conditions for its permissibility.