Sunan ad-Darimi

Sayyiduna Abdullah bin Mas’ud (may Allah be pleased with him) narrated from the Prophet Muhammad (peace and blessings be upon him) in a marfu’ (elevated) report that the worst of those who convey are those who convey lies, and lying is not permissible in any situation, whether seriously or in jest, and a man should not make a false promise to his son which he cannot fulfill. Truthfulness leads to righteousness, and righteousness leads to Paradise, and lying leads to wickedness, and wickedness leads to Hell. It is said about a truthful person that he has adopted truthfulness and followed the path of righteousness, and it is said about a liar that he has lied and committed wickedness (i.e., he has adopted the path of lying and immorality). A man continues to speak the truth until he is written with Allah as a truthful one (siddiq), and he continues to lie until he is written with Allah as a liar (kadhdhab). And the Prophet (peace and blessings be upon him) said to us: “Listen! Shall I not tell you what ‘adhah (heinous slander) is? It is tale-bearing that creates discord among people.”