Sacrifice is an important word of religion and spirituality too, of ancient Indians.
The rituals and rites associated with sacrifices were ruling during earlier times of Indian religion. Sacrifice word was roughly equated with the rituals and rites conducted during the performance of sacrifice
The Upanishads have subtly handled and deftly deflected the meaning of and action associated with the word sacrifice; and said
"the most needed, sublime and relevant sacrifice towards spiritual life is sacrifice of ego; sacrifice of transcending phenomenal world ignoring its influences; ceasing to identify with them - the ego and influences of phenomenal world".
This expression of the Upanishads is the prime motto of all kinds of Vedanta, techniques and methods of meditation and Indian spirituality to attain serenity of mind, which is essential for a life of equanimity and responsibility to discharge responsibilities associated with human living and human endeavour.
Spirituality is like software. Religion is like hardware.
Wrong application of programming through hardware brings problems and difficulties.
Indian spirituality grew independent of existing social milieu and evolved to have an independent position different from parallel social and human endeavour of secular life.
Indian philosophy is not Indian religions. Indian philosophy is Indian spirituality.