Sandhyavandana.

Sandhyavandana (Sanskrit: संध्यावन्दन, sandhyāvandana) is a mandatory religious ritual performed, traditionally, by Dvija communities of Hindus[citation needed], particularly those initiated through the sacred thread ceremony referred to as the Upanayanam and instructed in its execution by a Guru, in this case one qualified to teach Vedic ritual. The Sandhyavandanam consists of recitation from the Vedas, accompanied by ritual. These rituals are performed three times a day- at morning (prātaḥsaṃdhyā), noon (mādhyāhnika) and evening (sāyaṃsaṃdhyā).

The Sandhyavandanam is the oldest extant liturgy in world religion. As a practice, it may be descended from the much older daily Agnihotra ritual.

Sandhyavandanam literally means "salutation to Sandhya". Sandhya, in turn, has traditionally been interpreted either as "the transition moments of the day" (namely the two twilights dawn and dusk), or as "the solar noon". Thus, Sandhyavandanam may be defined as the ritual "salutation to twilight or the solar noon".