Falsehood is the most difficult and damaging action a person can have from his tongue. Allah Almighty informs us about the fabricator of lies:
'It is those who do not believe in Allah’s revelations who fabricate falsehood. These are the liars.' (Surah an-Nahl, 105)
That is, he who does not believe Allah and His signs will invent a lie against Him. Because he is not afraid of suffering. He is a real liar. Since lying is a grave crime, a believer should not approach it.