פירוש על ויקרא 17:14

דמו בנפשו הוא means its blood represents its life (במקום הנפש), in as much as its life is depending on it.

THE BLOOD THEREOF IS ‘B’NAFSHO’ (ALL ONE WITH THE LIFE THEREOF). “Its blood represents its life, since life is dependent upon the blood.” This is Rashi’s language. But it is not correct.²⁰⁵From the language of Rashi it would appear that the substance of the blood is identical with the life of the animal, and that is not correct in Ramban’s opinion, since they are really two separate substances, and the blood of the animal is merely the “carrier” of its life. Hence Ramban will present other interpretations of the verse. Rather, it is possible to explain that the word b’nafsho here means “in its body,” Scripture thus stating, “for as to the life of all flesh, it is the blood in its body.” Similarly [we find the word nefesh meaning “body” in these verses]: ‘Nafsho’ (his person) was laid in iron;²⁰⁶Psalms 105:18. seventy ‘nefesh’ (persons);²⁰⁷Exodus 1:5. he [the Nazirite] shall not come near to a dead ‘nefesh,’²⁰⁸Numbers 6:6. meaning “a body,” since “the body” of anyone that is possessed of a nefesh (soul) is also called nefesh.
In my opinion Scripture mentioned three expressions with reference to blood, which constitute but one reason. First it stated, For the life of the flesh is in the blood.²⁰⁹Verse 11. Then it changed and said [in Verse 14 before us], For as to the life of all flesh, the blood thereof is all one with the life thereof, meaning to say that the blood is the life, and the life is in the blood, as both are mixed together, similarly to wine when diluted with water, in which case the water is in the wine and the wine in the water, and each one is “in” the other. Afterwards it explained [in the second half of Verse 14 before us, stating for the life of all flesh is the blood thereof], that the blood is the very life, meaning to say that both have become one inseparable substance, so that you can never find blood without life nor life without blood, as is known of the air²¹⁰The sense here is clearly “the force of the heart beat” pumping the blood. In Medieval learning it was explained as the element of air which originates in the heart, and which in turn supplies the blood and sustains the person. which originates in the heart, that it is the hyly²¹¹A Greek term indicating the primary matter created by G-d (see Vol. I, p. 23), and here used in a wider sense as the force in the heart which is the primary organ of life. from which proceed all dispositions [of man], supplying the substance which gives nutrition and makes blood, and it is the blood which in turn creates it and sustains it. [The relationship between life and blood is thus] like that of matter and form in all physical creatures, where the one cannot be found without the other. Now our Rabbis interpreted the three punishments of excision which Scripture mentioned with reference to blood²¹²Above, 7:27; 17:10, and 14. in the following way:²¹³Kerithoth 4 b. “One verse prohibits the eating of that blood with which life escapes [when cutting the throat of the offering, since it has been given for atonement upon the altar]; one verse prohibits the eating of blood which escapes when slaughtering [an ordinary, unconsecrated animal], and one verse prohibits the eating of blood, that [of a fowl or wild animal, which when slaughtered] must be covered.” This saying of the Rabbis explains why the punishment of excision was mentioned three times, but the reason for the different Scriptural expressions concerning the life and the blood [of the animal] is as I have explained.

כי נפש כל בשר דמו בנפשו הוא, “for the life-force of all living creatures is its blood” [or contained with its blood. Ed.] (a reference to the way the author described such an almost invisible essence in the blood in his commentary on verse 7).