Sahih Muslim
The Book of Virtue, Good Manners and Joining of the Ties of Relationship (Kitab Al-Birr was-Salat-I-wal-Adab)
Book Number: 032 / Hadith Number: 6308
'Abdullah b. Mas'ud reported Allah's Messenger (may peace be upon him) as saying: Telling of truth is a virtue and virtue leads to Paradise and the servant who endeavours to tell the truth is recorded as truthful, and lie is obscenity and obscenity leads to Hell-Fire, and the servant who endeavours to tell a lie is recorded as a liar. Ibn Abu Shaiba reported this from Allah's Apostle (may peace be upon him).