As it was already referred, lie originates from one of the mental weak points:

Sometimes, a man lies for the fear of poverty, people leaving him alone and loosing his position and rank.

Sometimes, he lies for the earnest to wealth, dignity, and other sensual desires, and uses this illegitimate means for achieving his purpose.

Sometimes, passions as well as excessive love and hatred cause a man to say untruth in favor of one who loves or against one who is hated by him.

Once he lies in different scientific, historical and such like issues for showing himself more than what he really is and expressing science and knowledge.

But all of these vicious attributes, which are the sources of lie, actually originate from one's low personality and weakness of spirit and belief.

Those who do not believe on their own personality, and have a feeble and humble spirit, resort to lie, falsification, fraud and treachery for gaining their purposes and escaping losses. In contrary, powerful and high personality individuals rely on their own personality and ability, and seek their victory thereon.

Moreover, those having a perfect belief on divine everlasting power, and considering His dominant will as the source of all blessings, victories and successes, have identified His power beyond all powers and His support beyond all supports, do not have any reason for resorting to untruth and lying for gaining a benefit or escaping a loss.

And sometimes this dangerous vice roots in man for inattention to the disadvantages of lie and importance of truthfulness, and unhealthy family, or environment of society and associates.

One of the other important factors in lying is feeling low personality and inferiority complex. Those who are affected to such complex, try to compensate it with all types of lie, exaggeration and self-glorification.