What is the ruling on writing "Goods sold are neither returned nor exchanged" on invoices, and is this condition permissible in Islamic law?

Selling goods with the condition of no return or exchange is impermissible, as it involves harm (ḍarar) and ambiguity (ta‘miyah). The seller's intention is to obligate the buyer to the merchandise, even if it is defective. This condition does not absolve the seller of defects, so the buyer has the right to exchange it or receive compensation for the defect (arsh al-‘ayb), because the price is in exchange for a sound product. The seller taking the price despite the defect is taking it unjustly. The Sharia has established customary conditions (al-sharṭ al-‘urfī) as equivalent to verbal ones for safety from defects, thus allowing return upon the discovery of a defect.