Allah Most High says, {Woe to those that deal in fraud, those who, when they have to receive a measure from men, exact full measure, but when they have to give a measure or weight to men, give less than due. Do not they think that they will be raised upon a Mighty Day, a day when (all) mankind will stand before the Lord of the worlds?} (AI-Mutaffifeen: 1-6)

As-Saddiy said the reason of revelation of the above Ayah traces back to Prophet's arrival at Medina where he found a man called Abu Juhainah who had two scales, one for giving and the other for receiving.

The Prophet (pbuh) said, "Five entail five. They asked, what do you mean, Messenger of Allah? He said, II whenever a group of people break a covenant, Allah will entice their enemy to attack them. Whenever, they rule by other than Allah's revelation they will be plagued by poverty. If indecency prevails, they will be afflicted by many deaths. If they cheat when weighing Allah will withhold their pasture-lands (or pasturage) and they will face barren years. If they do not pay Zakat, Allah will deprive them of rain.” Malik Ibn Dinar said, once one of my neighbors came to me suffering from a deadly disease saying! “Two mountains of fire, two mountains of fire”. “What do you say”, I asked. He said, Abu Yahya, I had two scales, one for giving and the other for receiving. Malik Ibn Dinar, said, I, therefore, crush them with one another. Thereby the man said, the more you crush them, the more suffering I get, Abu Yahya.

Afterwards, the man died affected by illness.

Cheating when weighing or measuring out goods is considered as a type of theft, a breach of faith and consuming other's property through falsehood. Allah promises to punish such people with wail which may be interpreted as a severe torture or a valley in Hell-Fire. This valley is so hot that it can melt all the mountains of the world.

One of the early Muslims said, I testify that all those who weigh or measure will enter the Hell-fire.

This is because; none can measure justly save those whom Allah protects. Another one said, once I visited a sick man suffering from the death trials. Thereby, I began to instruct him to say the testification of faith, but he could not speak. When he became conscious, I asked him, why did not you repeat the testification of faith? He answered, O brother, the scale's blade was upon my tongue and prevented me to speak.

Thereupon, I asked him, did you give short weight? He said, never. But, I used not to wait for a while after weighing to check. Behold! This is the abode of those who do not check their scales. How about those who give short weight.

Nafi' narrated that Ibn 'Umar who when passing by a seller used to say, “'fear Allah and give just measure or weight.” This is because the cheaters when weighing or measuring will be bridled by sweat up to half of their ears on the Day of Judgment.

Some of the early Muslims said, woe to those who give short weight to others even a seed less in return for Paradise. Whose width is that of the whole of the heavens and the earth? Woe to those who take over weight from others even a seed over (if the buyer is the one who weights)