Mahabharata upholds Satya as the most important teachings of Santana Dharma. It says – ‘Satya is always the righteousness of good people; satya is eternal dharma (Satyam satsu sada dharmah satyam dharmah sanatanah – Shanti Parva 162/4).
In the Yaksha-Yudhisthira samvad (dialogues), when asked by Yaksha, ‘On what is the Sun established?” Yudhisthira answered, ‘On Satya’, (Vana Parva 3/3/46). Similarly, in reply to the question, “What is the single provision of place in swarga (heaven)?” Yudhisthira said, ‘Satya.’ (Vana Parva 3/3/69).
The Mahabharata says that the essence of Veda is satya, and the essence of satya is control of the mind and senses (Vana Parva 207/67). It also says that kingdom, children, fame and wealth, these all are not even equal to the sixteenth part of satya (Vana Parva 34/22).
Dharma is protected by truth (Udyoga Parva 34/39).
Satya is dharma, dharma is light, and light is pleasure. Asatya is adharma (unrighteousness), adharma is darkness, and darkness is pain or sorrow. There is no dharma (righteousness) above satya and no sin more heinous than the anrta (lie) (Vana Parva 162/24).
Satya is Brahman, satya is penance, creatures get created from satya, the world is sustained by satya, and one goes to swarga (heaven) by satya (Moksha Parva 190/1). There is no penance greater than satya (Moksha Parva 175/35).
Satya or truth is the greatest wealth of the rishis, and for the kings there is no greater cause of trust than satya (Shanti Parva 56/18).
Puranas propagated the glory of satya through their stories. The story of Satyanarayana vrata and the story of King Harishchandra of Ayodhya are so famous that they have become an important religious ceremony and Satya Harischandra has become an idiom of truthfulness.