Among the various types of Vedic sacrifices, the Somayāga is an important one. It derives its name from the fact that the juice of the soma creeper is used as oblation. This juice is pressed out of the creepers by stones or mortar and pestle, and is purified by being passed slowly through a strainer of sheep’s wool. It is then transferred to jars and mixed with milk.
There are three savanas or press-ings—morning, noon and evening, known respectively as prātas-savana, mādhyan-dina-savana and tṛtīya-savana.
The Bahiṣpavamāna is the stotra or hymn that is chanted during the prātas-savana. Since it is outside (bahir = outside) the sadas or the assembly hall, it is called Bahiṣpavamāna.
It consists of three tṛcas or triplets of Ṛgvedic mantras (9.11.1-3; 9.64.28-30; 9.66.10-12) making a total of nine verses. These verses are sung as Sāmans (Sāma-vedic chants) in a special style called ‘trivṛt’ wherein the first verse of each triplet is chanted first followed by the second and the third. If the verses of each triplet are symbolically represented as a,b and c, the scheme of chanting will be thus: a1+a2+a3; b1+b2+b3+; c1+c2+c3.
In sum, these verses welcome the deity presiding over the soma juice, beg him to protect the family and property of the sacrificer and describe the graceful flow of the juice through the strainer.