Likewise, anyone who is unaware of the value of goods must not be misled or deceived—for example, by being quoted an unusually high price so that he will offer something close to it. Rather, he should be sold the goods in accordance with customary, acceptable practice. And Allah knows best.”

He was asked:

“What is the ruling on selling to a trusting buyer?”

He replied:

“A trusting buyer must be charged only the price charged to others. No one in whom a buyer places his trust may overcharge him by taking a profit beyond customary bounds. Some scholars have set this threshold at one third, and others at one sixth.

Others have said that customary practice is the standard: whatever profit sellers normally make from buyers who bargain, they may also make from a trusting buyer.

A trusting buyer has been defined as someone who does not bargain, but simply says, ‘Take your payment and give me the goods.’ He has also been defined as someone who is unaware of the value of the goods. Neither may be grossly overcharged. A hadith states:

‘Overcharging a trusting buyer is usury.’

Anyone known to overcharge such buyers deserves punishment. Indeed, he must be barred from trading in the Muslims’ marketplace until he commits himself to obeying Allah and His Messenger. The overcharged buyer may rescind the sale, return the goods, and recover the price paid. If this unjust seller who overcharges people repents but cannot restore to those he wronged what is rightfully theirs, he should give in charity an amount equal to what he took from them through wrongdoing and overcharging;