No man, however careful, can avoid sins of omission and commission in life. Recognizing this fact, the Hindu dharma-śāstras have provided for prāyaścittas (expiations) by performing which, these sins can be obviated, or at least, their effects can be minimised. Aghamarṣaṇa-vrata is such a prāyaścitta prescribed by even the most ancient dharmaśāstra works like those of Gautama, Baudhāyana, Manu and Yājñavalkya, as an omnibus penance for all types of sins.
The person performing it must fast for three days, recite the Aghamarṣaṇa-sūkta three times every day at the time of bath, standing in the water of a river or tank or pond, spend the days standing and nights, sitting. At the end of the vrata he should gift a milch-cow. This penance is said to be equal in sanctification to the avabhṛthasnāna (ceremonial bath) taken at the end of an Aśvamedha sacrifice.