Whatever you offer to God or Vishnu is called sacrifice. Whatever we do here, within this material world, is some sort of sinful activity, even if we do not kill willingly. When you walk down the street you are killing many animals. Whenever you drink water, you are also killing. Below a water pot there are many ants and microbes that are being killed. Whenever you light a fire, there are many small microbes that also burn in the fire. When you grind spices many small microbes are killed. We are responsible for this. Willingly or unwillingly, we are becoming entangled in many sinful activities. Therefore, Bhagavad-gita says that if you take the remnants of foodstuff after offering sacrifice, you become freed from all contamination. Otherwise, one who cooks to eat personally without offering to Krishna is simply eating sinful reactions. This is our position. Therefore, it is stated that because people generally cannot control their senses, they engage in the materialistic way of life in which repeated birth and death in different species takes place.
Ref >> Srila Prabhupada Vani