Dishonesty and lying in the light of Islam

A very common saying is 'Honesty is the best policy'. On the other hand when it come to our social life and relationships, lying and dishonesty sometimes becomes a major sin. It is also said that it is the root of every evil.
Why lying and dishonesty is a major sin and what scholars say about lying and dishonesty?

It may take care of the present, but it has no future. Worse than telling a lie is spending the rest of your life staying true to a lie. ~Robert Brault
We tell lies when we are afraid-----, afraid of what we don't know, afraid of what others will think, afraid of what will be found out about us. But every time we tell a lie, the thing that we fear grows stronger. ~Tad Williams
Lying and dishonesty always leads to hypocrisy.