"Where was he, who thus established us? He Is within the mouth; hence is
Ayasya. He is Angirasa, because he is the essence of the members."
Brihat Aranyaka I-3-8.
Commenting on this passage Sankaracharya says: "Life is also called
Angirasa, the essence of causes and effects. Angirasa is a compound of
Anga and Rasa -- Anga meaning members, causes, and effects, and Rasa
essence, substance; the whole meaning therefore is the substance, upon
which causes and effects depend -- It is the essence of every thing,
because unless it were present, all would become without effect."
"He who abides in the mouth is Angirasa, for he is the essence (Rasa) of
the members (Anga). Life is the essence of the members. This is also
Brihaspati. Speech is Brihati. Life is the preserver (_pati_) of
Brihati, therefore it is Brihaspati."
B.A. I-3-19 and 20.
Brihaspati or the presiding deity of the planet Jupiter is called
Angirasa _i.e._ the son of Angiras. The wife of Angiras is, according to
the Bhagavata, Sraddha or Faith, and, according to Vishnu Purina, Smriti
or Memory. The latter is a more suggestive name. Brihaspati or Jupiter
is the essence of all beings and of the Universe and is connected with
the memory of the past.
Angirasa is the Rishi of the 5th Mandala of the Rig Veda. The Mantras of
that Mandala are composed in the Brihati or big Metre. This accounts for
the name Brihaspati (Brihati+pati).
Brihaspati or Jupiter, as the guide of the Devas, has to play a most
important part in bringing about the life evolution of the present Kalpa
according to the records of the past and the essence or Rasa of all
beings. The Aranyaka therefore calls him life itself.
Utathya, another son of Angiras, is _u+tathya_. _U_ is an interjection,
used as an expletive -- _Tathya_ means reality, truth -- Utathya is said
to be an incarnation of Vishnu. Both the brothers are said to have
distinguished themselves in the Second Manvantara. _Sinivali_ is the day
preceding that of new moon or that day on which the moon rises with a
scarcely visible crescent. Kuha is new moon day when the moon is
altogether invisible.
_Raka_ is the full moon day.
_Anumati_ is the 15th day of the moon's age on which she rises one digit
less than full.
The full moon and new moon days have thus a mysterious connection with
the essence of all beings. On those days the herbs have their medicinal
properties in full and even men have mysterious potencies, which have
formed the subject of occult study.