The Vedas, which were originally only available in oral form, but eventually written down, are the earliest sacred books of Hinduism. The name means "knowledge" or "sacred lore." Scholars date the earliest versions of the Vedas to about 1500 BCE. However, Hindus consider them to be more ancient. They say that Vedas are vishis, holy men of the distant past, who did not create the Vedas, but heard them and transmitted them to later generations.
The four basic sacred text collections that made the Vedas include:
1) the Rig Veda, a collection of more than a thousand chants to the Aryan gods;
2) the Yajur Veda, which contains matter for recitation during sacrifice;
3) the Sama Veda, a handbook of musical elaboration of Vedic chants; and
4) the Atharva Veda, which consists of practical prayers and charms, such as prayers to protect against snakes and sickness.
The Rig Veda, the most important of the Vedas, has an account of the origin of the universe.
The Upanishads are later works that express philosophical and religious ideas that arose in introspective and meditative traditions. The Upanishads comprise about a hundred written works that record insights into external and internal reality. Unlike earlier Vedic material, the Upanishads tell us that a person who has the necessary experience can be a spiritual master. The Upanishads are written in dialogue form, appearing as both prose and poetry.
There are several important concepts in the Upanishads, including Brahman and Atman.
Brahman means a divine reality at the heart of things. Brahman, the Supreme Spirit, is an invisible and subtle essence that is the Spirit of the whole universe. To experience Brahman is to know that every apparently individual reality in the world is actually a wave of the same sacred ocean of energy.
On the other hand, "Atman" means the deepest self. In Hindu belief, each person has an individual soul, and the individual soul confers uniqueness and personality. Everyone has a body, which is subject to alteration. However, in each person there is a reality more fundamental than changing individual characteristics. At the deepest level of "what I am" is a divine reality, and divine spirit that everything shares. It is true to say "I am God," because for the person who understands reality at its deepest level, everything is God.
Other concepts include maya, karma, samsara, and moksha.
Mahabharata - Bhagavad Gita
The Bhagavad Gita, which means “divine song," is part of a very long epic poem called the Mahabharata. The Mahabharata, written some time between 400 b.c.e. and 400 c.e., tells how the sons of Pandu conquered their cousins, the Kauravas, with the help of the god Krishna. The Bhagavad Gita was inserted at some time into this poem but has its
own identity and is often printed separately from the Mahabharata. The Bhagavad Gita, shaped by the priestly class between 200 b.c.e. and 200 c.e., has become a spiritual classic. It recalls themes from the Upanishads, but it also tries to strike a balance between mysticism and the practical needs of everyday life.
Like the Upanishads, the Bhagavad Gita is written in dialogue form. It occurs almost entirely between two figures: a prince, Arjuna, and his charioteer and advisor, Krishna.
Arjuna, a prince, feels that his power is being threatened by his cousins, the Kauravas. He has to choose between fighting to win back his rightful throne with his brothers or to accept his cousins as rulers. Arjuna wants to avoid violence, as it is hard for him because the Kauravas are also his family. He doesn't know what to do, and in the middle of the battlefield he casts aside his bow and arrows, overcome with sorrow. Krishna, his charioteer, tells the prince that action is needed, and that Arjuna must just do what is right, not what he desires or fears.