What is the ruling on selling an old spring mattress (with springs) for the purpose of selling the iron in it, given the difficulty of weighing it and the possibility of selling it without weighing, but with the potential for an inaccurate price estimation? Is it permissible to waive a right, even if the loss of that right is intentionally caused by the buyer, especially since the buyer might undervalue the price?
There is no harm in selling something for less than its market value as long as you are content, based on the prophetic saying: "Indeed, selling is by mutual consent."
There is also no harm in selling a mattress without knowing the weight of the iron springs inside it, even if these springs are the primary object of sale. Selling by estimation (Jazaf) is permissible due to need and necessity.
Summarized from the full answer at Ftawy · reviewed Sep 2, 2026
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