All praise be to Allah and peace be upon the Messenger of Allah, upon his family, his Companions, and those who follow him.
One day the Prophet (peace be upon him) went to the market, and while he was walking in the market, he stopped by a cereal seller then the Prophet (peace be upon him) put his hand in the cereals and found them wet.
Thereupon, he asked the owner of the cereal: What is this, O owner of cereals?
The seller said: "They became wet due to rain, O Messenger of Allah."
Thereupon, the Messenger of Allah (peace be upon him) said: "Would you put them above so as people could see its wetness, then he added: "The one who cheats is not of my followers." which is a discourse to the whole nation.
This is one of the Prophetic stories which contain multiple benefits, of which:
First, it is permissible for men to go to and walk in markets.
Second, the Messenger (peace be upon him) is a human being who eats as people eat, drinks as they drink, sleeps as they sleep, and walks in markets as they do. "And they say: Why does this Messenger (Muhammad peace be upon him) eat food, and walk about in the markets (as we)?" [Surat Al Furqan: 7].
Third, it is obligatory to enjoin good and forbid evils when someone sees a deniable act or a violation in markets, and he has to try to change it.
Fourth, the Prophet (peace be upon him) did not leave a good act but guided his nation to and did not leave an evil but warned his nation against, and one of the evils which he warned his nation against is cheating.
Fifth, an aedile should be sure of the crime before enjoining good and forbidding evil.
Sixth, the permissibility of field supervision for the officials to markets, launch inspection campaigns to shopkeepers, and ask them about the specifications of goods and their prices.
Seventh, the danger of cheating and explaining that it is one of the major sins because of the Prophet's saying: "is not one of us."
Eighth, prohibition of cheating by all types because of the Prophet's saying: "The one who cheats us is not one of us," so he made the matter absolute and did not limit it, generalized it without detailing.
Ninth, freeing oneself of wrong acts.
May Allah grant us success!
 This story was reported by Muslim in his Sahih (102).
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