Prohibition of Deceiving others
Abu Hurairah (May Allah be pleased with him) said: The Messenger of Allah صلى الله عليه وسلم said, "He who takes up arms against us is none of us; and he who cheats us is none of us.''
[Muslim].
Another narration of Muslim is: The Messenger of Allah صلى الله عليه وسلم happened to pass by a heap of corn. He thrust his hand in that (heap) and his fingers felt wetness. He said to the owner of that heap of corn, "What is this?'' He replied: "O Messenger of Allah! These have been drenched by rainfall.'' He remarked, "Why did you not place this (the drenched part of the heap) over the corn so that people might see it? He who deceives is not of us.''
Commentary:
1. To take arms here signifies to revolt against the Muslim community (and a Muslim government, for that matter) or draw a sword, gun, etc., to kill a Muslim - a common practice in the present-day terrorism.
2. Forgery and deceit have two different forms; one is implied and other is physical and visible. In the former, falsehood is given a veneer of truth. The latter is concealment of some defect, adulteration of some inferior quality merchandise in a superior one, addition of something to increase weight or volume or a substance by unfair means and other malpractices.
3. "He is none of us'' means "He is not following the way of Muslims'' or "His conduct is unlike that of Muslims.'' It is therefore, necessary for every Muslim to abstain from such evils.