Ahiṁsā means not arresting the progressive life of any living entity. One should not think that since the spirit spark is never killed even after the killing of the body there is no harm in killing animals for sense gratification. People are now addicted to eating animals, in spite of having an ample supply of grains, fruits and milk. There is no necessity for animal killing. This injunction is for everyone. When there is no other alternative, one may kill an animal, but it should be offered in sacrifice. At any rate, when there is an ample food supply for humanity, persons who are desiring to make advancement in spiritual realization should not commit violence to animals. Real ahiṁsā means not checking anyone’s progressive life. The animals are also making progress in their evolutionary life by transmigrating from one category of animal life to another. If a particular animal is killed, then his progress is checked. If an animal is staying in a particular body for so many days or so many years and is untimely killed, then he has to come back again in that form of life to complete the remaining days in order to be promoted to another species of life. So their progress should not be checked simply to satisfy one’s palate. This is called ahiṁsā.
Ref >> Srila Prabhupada Vani.