Sufiyan Bin Usaid relates that the Holy Messenger (peace and blessings of Allah be to him) said: No defalcation is greater than that you utter an incorrect word to a person who believes in your reliability. (Abu Daud)
This hadith is all about passing wrong information. Fanning rumours is one of the most hateful and undesirable deeds in Islam. The degree of this sin becomes greater when the person with whom you are passing the information believes in your credibility and reliability. In fact, Islam is the biggest promoter of truth and reality and it never allows its followers to resort to an inaccurate statement except in certain critical cases. Islam is too cautious about truth and reality to allow a person believing in all whatever others say.
Once the Messenger (peace and blessings of Allah be to him) said, a hadith in Muslim says: It will suffice for a man to become sinful that he narrates all what he listens from others. In the current scenario we see that even Muslims do not pay much heed to truth and at times they tell a lie so as to achieve some petty gains. Hence they put their eternal success at stake. Many say telling a lie is a minor sin. But the fact remains that telling a lie is not only a sin but also falls into the orbit of a fraud and defalcation. From another angle, how does one feel when one realises that one is being cheated by the person most reliable to him?