Is the showroom owner entitled to request an additional amount for ceramic tiles that were purchased and fully paid for six years ago, and left with him as a trust, knowing that the ceramic tiles chosen now have the same specifications, quantity, and measurements as the original ceramic tiles?

If a person buys an item and leaves it with the seller with his permission, it is a trust (amanah). If the seller then sells it, he is acting unlawfully (mut'addiyan), and he is obligated to guarantee a similar item if it is a fungible (mithli) item. Otherwise, he guarantees its value on the day of the transgression.

It is stated in "Al-Mawsu'ah al-Fiqhiyyah" (The Fiqh Encyclopedia) that if the destroyed item is fungible, it is guaranteed by a similar item. If it is non-fungible (qīmī), it is guaranteed by its value. Ibn al-Qayyim said that the principle is to guarantee destroyed items with items of the same type, to the extent possible.

The definition of a fungible item, according to Shaykh Ibn Uthaymeen, is that which has a perfectly matching or very closely matching equivalent. Accordingly, if the exact type is not found, he is obligated to provide something close to it in specifications and measurements. It is not permissible for the seller to demand a price difference because he is liable for the equivalent. The old price is not taken into consideration. What is due from him are specific meters of ceramic, so he is obligated to pay for a similar quantity or something close to it. If not found, he should pay its value at the time of the transgression.