Sayyiduna Ibn Mas'ud (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Guard yourselves against lying, for lying leads to sin and sin leads to the Fire. A person continues to lie and pursues falsehood until he is written with Allah as a «كذاب». And adhere to truthfulness, for truthfulness leads to righteousness and righteousness leads to Paradise. A person continues to speak the truth until he is written with Allah as a «صديق»."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 4108