1. If an item has a defect, the seller should disclose it to the purchaser. It is not permissible for him to conceal the defect.
عن أبي هريرة أن رسول الله صلى الله عليه وسلم مر على صبرة طعام فأدخل يده فيها، فنالت أصابعه بللا فقال: ما هذا يا صاحب الطعام؟ قال أصابته السماء يا رسول الله، قال: أفلا جعلته فوق الطعام كي يراه الناس، من غش فليس مني. (مسلم رقم 102)
Hazrat Abu Hurayrah (Radhiyallahu Anhu) reports that on one occasion, Rasulullah (Sallallahu Alaihi Wasallam) passed by a heap of grain. He then inserted his hand in the heap (to inspect the quality of the grain at the bottom) and found that the grain was moist. He asked the owner of the grain, “What is this?” The owner replied, “O Rasulullah (Sallallahu Alaihi Wasallam), the grain became moist due to the rain.” Rasulullah (Sallallahu Alaihi Wasallam) replied, “Then why did you not place it (the moist grain) on top of the heap so that the people can see the defective grain (that you are selling to them).” Rasulullah (Sallallahu Alaihi Wasallam) then said, “The one who deceives (people) is not from me.”