Answer: Lying is the opposite of truthfulness and it means not telling the truth. Examples include: lying to people, not keeping promises, and false testimony.

The Prophet (may Allah's peace and blessings be upon him) said: "Lying leads to wickedness and wickedness leads to Hellfire. A man will keep telling lies until he is recorded with Allah as an utter liar." [Agreed upon] The Prophet (may Allah's peace and blessings be upon him) also said: "There are three signs of a hypocrite", and he mentioned among them: "When he speaks he lies, and when he makes a promise he breaks it". [Agreed upon]