Man aspires after maximum happiness but with minimum effort, if he can help it. This aspiration can often tempt him to resort to shortcut methods which will entail a lot of suffering to other beings. The Vedic ṛṣis (sages) who had thoroughly understood human psychology, propounded and propagated a system of sacrifices by following which man could get his desires fulfilled, in a righteous way.
Every such sacrifice must have a minimum of four priests: hotā, adhvaryu, udgātṛ and brahmā. Adhvaryu, the second priest who follows the Yajurveda, is by far the most active of the group. It is he who surveys the sacrificial ground, designs and builds the altars, prepares or secures the utensils, cooks the sacrificial oblations, fetches water and wood, kindles the fires, brings the animals and immolates them, all the while repeating the appropriate mantras from the Yajurveda at appropriate times. Being constantly on the move, he has no fixed seat. He is normally assisted by three priests: pratiprasthātṛ, neṣṭṛ and unnetṛ. Sometimes the number of such priests including him may be as large as 36.