They show how honesty and sincerity bring blessings to transactions, while lying and deception eradicate them. Being sincere and honest includes showing a buyer or a tenant any hidden faults and telling them the real price or bid.
Cheating and deceit include falsely increasing the purchase or bid price to make the buyer or tenant pays a like amount or close to it.
It is related in the Two Sahih Books of Hadithon the authority of Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace be upon him) said, "Three persons whom Allah shall neither speak to on the Day of Resurrection, nor look at, nor purify, and they shall have a painful torment: A person who has spare water in a desert and he withholds it from the wayfarer. A man who bargains with another man over a commodity after the 'Asr (Afternoon Prayer) and swears to him (falsely) by Allah that he has been offered suchandsuch (a price) for it and he (the buyer) believes him to be true though he is not. And a man who swears allegiance to a ruler, only swearing allegiance to him for the sake of this world (material gains); if he gives him of it, he fulfills his obligation; and if he does not give him, he does not fulfill it."
It is obligatory on all Muslims to have Taqwa (fearing Allah as He should be feared) in their transactions and to beware of doing anything that brings about Allah's Anger and His Severe Punishment with which He has threatened to chastise those who cheat, deceive, and lie. It is also obligatory that Muslims should advise one another to be truthful, sincere, and have Taqwa in all their affairs, because this will result in happiness in this world and in the Hereafter, purity of hearts, and a sound society. They will also bring blessings in transactions and security from involvement in illgotten gains and doing injustice to another Muslim.
It is authentically reported that the Prophet (peace be upon him) said, "One believer to another is like the parts of a building, each supporting the other." And he (peace be upon him) interlaced his fingers. He (peace be upon him) also said, "The similitude of believers in regard to their mutual love, mercy, and empathy is that of a body; when any of its parts suffers, the whole body calls upon one another (sharing) with (it) sleeplessness and fever."
I ask Allah (may He be Praised) to set aright the Muslims' affairs, to join their hearts in piety, and to guide their rulers. May Allah grant us truthfulness and sincerity in all our affairs and help us to cooperate in righteousness and piety; for, indeed, He is the Most Generous, the Most Bountiful. Peace and blessings be upon our Prophet Muhammad, his family and his Companions.