Islam has stressed and asserted the importance of honesty in monetary dealings and highlighted its vital role in social stability and peacefulness.
The Holy Qur’an and Prophet Mohammad (PBUH) have made it clear to us that the true Muslim is he who is honest and upright in his business and monetary dealing with others, even if they weren’t Muslims. Also the true Muslim should keep his word and fulfill his promises, shun fraud and avoid deceit and perfidy, encroach not upon the rights of others, nor take part in wrongful litigation. Also a good Muslim does not give false testimony, and abstains from making unlawful money as from usury and graft. According to Islam whoever is not free from these vices is not a true believer but a renegade and a worthless transgressor.
And the Qur’an is rich with verses that confirms all this. Allah says in the Qur’an:
"Oh ye who believe! Eat not up each other's property by unfair and dishonest means." Qur’an (4:29)
Allah forbids all unclean and corrupt means of making money, such as, dishonest trading, gambling, and bribery. And the Holy Qur’an has explained and described such practices in many of its verses. In this verse, for instance, Allah warns those traders who cheat in weighing, he says:
"Woe to those that deal in fraud, - those who, when they have to receive by measure from men, exact full measure, but when they have to give by measure or weight to men, give less than due. Do they not think that they will be called to account- on a Mighty Day when (all) mankind will stand before the Lord of the Worlds." Qur’an (133: 1-6)
Another example is given in the coming verse, where Allah urges Muslims to be very particular about their trusts and about other people's rights.
"Allah does command you to render back your trust, to those to whom they are due." Qur’an(4:58)
At two places in the Qur’an a chief distinguishing feature of Muslims is said to be that they are:
"Those who faithfully observe their trusts and their covenants." Qur’an (24:8)
Prophet Mohammad (PBUH) has stressed the importance of honesty in most of his sermons, saying:
"Remember, there is no faith in him who is not trustworthy; there is no place for him in religion who cares not for his pledged word or promise."
He (PBUH) also said:
“The signs of a hypocrite are three: when he speaks, he is false, when he promises, he fails; and when he is trusted, he plays false."
Condemning those who cheat in business Prophet Mohammad (PBUH) has said:
"He who cheats is not of us. Deceitfulness and fraud are things that lead one to Hell."
Once Prophet Mohammad (PBUH) came upon a heap of corn in the market of Madinah and thrust his hand onto it. His fingers felt damp. On being asked, the trader replied that rain had fallen upon it. The Prophet (PBUH) observed,
"Why did you not then keep (the wet portion of) it above the dry corn, so that men may see it? He who deceives, is not one of us."
Thus traders who deceive by showing to customers a false sample or by concealing from them the defects of the product they’re selling are not true Muslims in the judgment of Allah Prophet (PBUH) and, they are going to end up in hell.
Another example: Prophet Mohammad (PBUH) said:
"The seller must explain to the buyer the defects, if any, in the quality of the article offered for sale. Should this not be done, the seller will permanently be caught in the Wrath of Allah (according to another narrator the exact words, ‘he will always be cursed by the angels')."
In short, all manner of deceit and dishonesty in business is prohibited in Islam. It has been proclaimed to be an act worthy of unqualified condemnation. The Holy Prophet has expressed his strong dislike for those who do so. He has said he will have nothing to do with them; they do not belong to him.
Likewise, bribery and usury, although might be practiced by mutual consent and agreement, are totally prohibited and forbidden and those who are guilty of them have been condemned by Allah and His Prophet (PBUH). Prophet Mohammad (PBUH) said:
"The curse of Allah rests on him who offers loan on usurious terms, and on him who receives, and on those who are witnesses to the transaction, and on the writer who writes the deed thereof."
As for bribery, Prophet Mohammad (PBUH) according has "condemned alike the giver of bribes, and the taker of bribes in deciding cases."
Prophet Mohammad (PBUH) said:
"If a person made a recommendation for anyone in a just manner and gratified party gave him something as a gift (in return for it) and he accepted it, then he committed a grave error (meaning that it, too, is a form of bribery)."
Usurpation of another's property by force or fraud or dishonest litigation is even worse. Prophet Mohammad (PBUH) made this clear, as he says:
"Whoever occupies land belonging to another unjustly will be sunk into the ground along with the plot of land on the Doomsday till he reaches the lowest layer of the earth."
"He who acquires the property of a Muslim unjustly by taking a false oath (before an Officer) is debarred by Allah from entering Paradise and the Fire of Hell is made inevitable for him."
Prophet Mohammad (PBUH) again, is reported to have warned a person who was very fond of entering into litigation with others in these strong words:
”Remember, he who will obtain the property of another by swearing a false oath will appear as a leper before Allah (on the Day of Judgement).”
And, again he (PBUH) said:
“Whoever laid a claim on a thing that was not his is not of us.”