Rashi on Leviticus 17:11/רש"י על ויקרא י״ז:י״א

1כי נפש הבשר FOR THE LIFE OF THE FLESH of every creature, not only of animals brought as sacrifices, is dependent on its blood (בדם היא), and it is for this reason that I have placed it [on the altar] to make expiation for the life of man: let life come and expiate for life!