The ritual of agnyādhāna (agnyadhana) is also known as agnyādheya (agnyadheya). This ritual used to be held grandly from the Vedic age to the age of Mahābhārata (Mahabharata). This ritual saw the gathering of araṇi (arani; firewood) from a few days before the ritual. After that, the yajamāna (yajamana; the host of the worshipping ritual) used to welcome the priests with madhuparka (a ritualistic bowl with certain ingredients in it). Then, cleanin up the place of worship, along with his wife the householder got ready for the ritual of agnyādheya. On the assigned day, when the Sun reached its zenith, adhvaryu, the priest of Yajurveda, used to light another fire from the aupāsana (aupasana) hearth, cook a mixture of rice and ghee (known as brahmaudya), divided this brahmaudya into four portions and kept the portions in four places. This was eaten by all the priests.
It is believed that meat, too, was consumed in this ceremony; because the fat of a cow (or of a goat, in case of absence of a cow) tied up from a day prior to the ritual was offered as an oblation in Agni (the Fire-god). After the place of yajña (yajna) was cleaned up and is was past midnight, adhvaryu used to light a fire by rubbing together two pieces of araṇi. This was accompanied by the chanting of hymns from Ṛgveda (Rigveda) or singing of hymns from Sāmaveda (Samaveda). The fire thus produced was held in a vessel, taken to the room of the householder and set up in the hearth of gārhyapatya Agni. This entire ritual was known as agnyādhyāna and this fire was used to light the gārhapatya and the dakṣiṇāgni fires.
[Kātyāyana Śroutasūtra(weber) 4.7.1; to 4.9.9;
Āpastamva Śroutasūtra(Garbe) 5.3.17-20]
Notwithstanding the number of rituals and yajña prevalent, Mahābhārata is completely aware of the fact that agnyādheya was the primary need of a householder. In Śāntiparva (Santiparva) of Mahābhārata, Arjuna, while requesting Yudhiṣṭhira (Yudhishthira) to take the throne, said, “Who can be more pious than the householder who performs agnyādheya everyday, that is performs the ritual of agnihotra in the fire set up with his own hands?” Those who do not reverentially pay the priests their fee (dakṣiṇā; dakshinaa) after performing the ritual of agnyādheya have been called anāhitāgni (anahitagni) in Mahābhārata. This fire of agnyādheya, which was set up by a couple after their marriage, needed to be carried ahead of the corpse at a funeral procession. In cases of demise of Rāmacandra (Ramachandra) as well as Rāvaṇa (Ravana), the fire of agnihotra was carried along with them.
In the Vedic age, a householder abiding by the Vedic commandments, used to construct a hearth for Agni in his house. After leading the life of a celibate in the house of his Guru (i.e. after spending the first quarter of life or brahmacarya), a person used to return to his house and undergo the Vedic rituals of marriage to become a householder and enter the second quarter of his life, namely gārhasthya (garhasthya). He then constructed the fire-shed (including a hearth) within his house and set up śrauta fire therein. The procedure of establishing the holy fire by a newly married man within his own house was known as agnyādhāna or agnyādheya. It has been said that a brāhmaṇa yajamana should perform agnyādhana at his home during the spring season, the kṣatriya (kshatriya) during summer and vaiśya (vaishya) during monsoon – vasante brāhmaṇo’gnīnādadhīta, grīṣme rājanyo, varṣāsu vaiśyaḥ. This ritual of agnyādhana, which marked the beginning of the household life, needed the presence of a horse which symbolized the victorious cortege of the ancient Aryan race.