The Mundaka Upanishad, in Chapter One: Section 2 has a series of verses describing the act of the sacrifice. Most commentators interpret this in a strictly external sense and describe the forms of the ritual sacrifice. Sri Aurobindo, in The Secret of the Veda, has described the ;symbolism of the language of the sacrifice and its true relation to the aspiration of mankind:
“The Vedic sacrifice is, psychologically, a symbol of cosmic and individual activity become self-conscious, enlightened and aware of its goal. The whole process of the universe is in its very nature a sacrifice, voluntary or involuntary. ” (Sri Aurobindo, The Secret of the Veda, pg. 266)
Verse 2 of Chapter 1: Section 2 of the Mundaka Upanishad is translated by Sri Aurobindo: “When the fire of the sacrifice is kindled and the flame sways and quivers, then between the double pourings of butter cast therein with faith thy offerings.”
The fire is the conscious divine will, Agni, the “knower of all things born”, manifested in the human being as aspiration for the divine truth of existence and the meaning of life. When this aspiration is awakened it is not constant nor steady to begin with and thus needs to be supported and reinforced constantly. The “double pourings of butter” represent, as Sri Aurobindo has described in The Secret of the Veda, the working of the clarified mind. With a clarified mind, one must then make the offerings with faith. The offerings of the human being are the thoughts, the feelings and the actions in life. All life becomes the sacrifice and all one’s actions become the offerings.
The Mundaka Upanishad thereby describes the process of spiritual growth to be undertaken by the awakened human being through application of the powers of the mind, the will, the heart and the actions of the vital life force.
Sri Aurobindo, The Upanishads, Mundaka Upanishad, pp. 193-210