A thing that comes to you in an illegitimate manner is haram or taboo. If one acquires bread by cheating someone or he has usurped it from someone, or has bought it from the proceeds of usury, or has consumed without the knowledge or permission of the rightful owner, then he has contravened the rules of Shariah. This is a haram act.

The next in line of impure foods is the murdar or the meat of an animal that has not been slaughtered properly as required by the Shariah. This applies also to those animals eating of whose meat is permissible in the Islamic Shariah. For example, if a person, while slaughtering an animal, doesn't intentionally say the words Bismillah before putting the knife to the throat of the animal, eating of such meat is taboo. Allah says in the Holy Quran, "Don't eat that thing on which Allah's name has not been uttered". Therefore if a halal animal is slaughtered without saying Bismillah, consumption of such meat is forbidden.
Syed Taoos has recommended application of this verse to all foods, although the verse pertains only to animal foods. Syed Taooks says," All the eatables that are prepared without taking the name of Allah before commencing the preparation, I don't partake of! How can a momin eat the bread that has been cooked by the baker without taking the name of Allah."