It is narrated from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "A person continues to tell lies until he is written as a «كذاب» with Allah, and a person continues to speak the truth until he is written as a «صديق» with Allah."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 4095