Veda is the most ancient sacred literature of Hinduism, of individual books belonging to that literature. This body of ancient literature consists primarily of four collections of hymns, detached poetical portions and ceremonial formulae. The collections are called the Rig-Veda the Sama-Veda, the Yajur-Veda, and the Atharva-Veda. They are known also as the Samhitas (roughly “collection”).
The four Vedas were composed in Vedic, an early form of Sanskrit. The oldest portions are believed by scholars to have originated largely with the Aryan invaders of India some time between 1300 and 1000 bc; however, the Vedas in their present form are believed to date only from the close of the 3rd century bc. Before the writing down of the present texts, sages called rishis transmitted the Vedic matter orally, changing and elaborating it in the process. Large masses of material probably taken from the original Aryan milieu or from the Dravidian culture of India were preserved, however, and are distinguishable in the texts.
The first three Samhitas are primarily ritual handbooks that were used in the Vedic period by three classes of priests who officiated at ceremonial sacrifices. The Rig-Veda contains more than 1,000 hymns (Sanskrit rig), composed in various poetic metres and arranged in ten books. It was used by the hotri, or recites, who invoked the gods by reading its hymns aloud. The Sama-Veda contains verse portions taken mainly from the Rig-veda. It was used by the udgatri, or chanters, who sang its hymns, or melodies (Sanskrit sama). The Yajur-Veda, which now consists of two recessions, both of them partly in prose and partly in verse and both containing roughly the same material (although differently arranged), contains sacrificial formulae (Sanskrit yaja, “sacrifices”). It was used by the adhvaryu, priests who recited appropriate formulas from the Yajur-Veda while actually performing the sacrificial actions. The fourth Veda, the Atharva-Veda (in part attributed by tradition to a rishi named Atharvan), consists almost exclusively of a wide variety of hymns, magical incantations, and magical spells. Largely for personal, domestic use, it was not originally accepted as authoritative because of the deviant nature of its contents. Scholars believe that it dates from the remnant of the indigenous pre-Aryan culture. Eventually it was acknowledged as one of the Vedas, especially after its adoption as a ritual handbook by the Brahmins, the fourth and highest class of priests officiating at the sacrifices.
Strictly speaking, the Vedas include the Brahmanas and the mantras. The former are prose commentaries attached to each of the four Vedas and are concerned principally with the details and the interpretation of the sacrificial liturgy. The latter are the poetic stanzas of the four Vedas, mantra being the term used specifically for the four verse collections. The mantras are regarded by some scholars as the oldest part of the Vedas.
Supplementary to the Brahmanas are later esoteric works known as forest treatises, the Aranyakas were expounded and written by Brahman sages in forests because it was felt that a proper understanding of them could be achieved only in seclusion. The final portions of the Aranyakas are called Upanishads. Profound metaphysical and speculative works closely linked with the Brahmanas, they emphasize knowledge and meditation and are the first Hindu attempts at a systematic treatment of speculative thought. Vedanta and most other Indian philosophical systems developed from the Upanishads. The latest products of the Vedic period are the sutras (Sanskrit sutra, literally “thread”, roughly, “string of rules”). Collections of aphorisms elaborating and dissertating on the Vedic sacrifices, domestic ceremonies (such as marriage and funeral rituals), and religious and secular law, the sutras are significant for their influence on the development of Hindu law. As works of authority, they are not as highly regarded as the Vedas, Brahmanas, and Upanishads. The latter, especially the Vedas, are revered as apaurusheya (Sankrit, “not of human origin”).
More than the ideology, it is the development and fulfillment of thoughts and concepts from the Rig Veda that stand apart. The concept of the Primeval Man (Purusa) in the hymn Purusa Sukta is echoed in the Svetasvatara Upanishad; the Hiranya garbha of the Upanishads is the effect Brahman, the karya Brahman (the world Soul), the one mentioned in the Hymn of Creation of the Rig Veda, while the unchanging one is Isvara, the causal Brahman (kirana Brahman) i.e. the eternal God.