Deceiving the customer and telling him that the price of the item is fifty, and that the price has been reduced to thirty for a special occasion, such as `Eid for example, even though there has been no reduction at all, is clearly lying.

It is permissible for a Muslim to enter into a business partnership or work with a disbeliever or an evildoer. The Messenger of Allah gave Khaybar to the Jews to work the land and cultivate it, in return for which they would have half of its yield.