Lying is a very bad habit, addictive and generally self destructive, most importantly it is (under nearly all circumstances) something which God detests us to do.
Mendacity resembles a violent blow,
the scar of which remains,
though the wound may be healed.
See you not how the brothers of
Joseph became noted for falsehood,
and no trust in their veracity remained,
as Allah the most high has said:
Nay but ye yourselves
have contrived the thing for your own sake.
One habitually speaking the truth
Is pardoned when he once makes a slip
But if he becomes noted for lying,
People do not believe him
even when he is speaking truth.
Lying is nearly always a harmful and destructive trait, it is the act of stealing the truth from one whom we are talking to.
There are rare occasions where it is not sinful to lie, these are when greater harm would be caused by the truth – yet in normal daily life lying should be avoided as it is something God dislikes which harms the soul of the one who does it – particularly as it becomes and addictive habit that often leads to all sorts of problems.
This does not mean that people should go around revealing all their faults to people – indeed it is meritorious to cover one’s faults – it means that we should not set out to deceive others without exceptional (and this truly means exceptional) causes.
God Almighty says in the Holy Qur’an;
And whenever you give your oath,
say the truth
(Surah al-An’aan 152)
When a person follows after unrighteousness,
Where will he find deliverance on the day of judgement?
Whosoever assumes the habit
of false speaking
Has no splendour for
the lamp of his soul.
Falsehood puts a man to shame,
Falsehood deprives a man of dignity.
A wise man blushes at a liar,
Since no one esteems such a person.
O brother! beware that you speak not falsely,
For a liar is despised and without repute.
Nothing is worse than unrighteousness;
O son! There from arises loss of fair name.