Sometimes some persons tend to indulge in petty thefts. This is derived from previous lives spent as a cat. Similarly, the vacillating and fickle nature displayed by a person may be attributed to a previous life as a monkey. Fickle-mindedness is characteristic of the monkey. Some persons are incurably ungrateful. They indulge even in harming those who help them. This is not a human trait. How, then, is it present in a man? It is because he must have been a serpent in a previous birth. The serpent is notorious for emitting poison even when fed on milk. So, an ungrateful person must have been a serpent in some previous life. One should offer therefore, at the altar of his mind, as a sacrifice his stubbornness, thieving propensity, ingratitude and pride. This is the Inner Yajna. Unfortunately, instead of performing sacrifices of this kind people treat goats and fowl as offerings. As a result the bad qualities continue to grow in man. It is to eliminate this evil sense of ingratitude that external sacrifices like Yajnas and Yagas have been recommended to man. Yajnas enable us to promote and refine the beneficent qualities in man. – Divine Discourse, Oct 10, 1983.