A yajamāna (one who performs a sacrifice) is expected to take dīkṣā or initiation at the beginning of the sacrifice he is undertaking. This is a purificatory ritual which imposes on him certain rules and code of conduct.
Sometimes, as a part of a major sacrifice, minor rites also will have to be performed. Some of these, considered as very important, require the yajamāna and his wife to take an additional dīkṣā. Such a dīkṣā, taken at the beginning of a subsidiary rite which itself is part of a bigger sacrifice, is called ‘avāntaradīkṣā.’ For instance in the Agniṣṭoma (a Soma-yāga), avāntaradīkṣā has to be taken before the pravargya rite. The yajamāna and his wife offer fuel sticks into the āhavanīya and gārhapatya fires respectively. Touching the water heated in the vessel called ‘madantī,’ the yajamāna clenches his fists closely, tightens his girdle and drinks hot milk. The dīkṣā ends with nihnava, a kind of salutation to heaven and earth, by the priests.
See also DĪKṢĀ.