Jami` at-Tirmidhi 1971

Abdullah bin Mas'ud narrated that the Messenger of Allah said:"Abide by truthfulness. For indeed truthfulness leads to righteousness. And indeed righteousness leads to Paradise. A man continues telling the truth and trying hard to tell the truth until he is recorded with Allah as a truthful person. Refrain from falsehood. For indeed falsehood leads to wickedness, and wickedness leads to the Fire. A slave (of Allah) continues lying and trying hard to lie, until he is recorded with Allah as a liar