John Gill Commentary Deuteronomy 12:23

"Only be sure that thou eat not the blood: for the blood is the life; and thou shalt not eat the life with the flesh." — Deuteronomy 12:23 (ASV)

Only be sure that you must not eat the blood
This is repeated again, that they might be careful to observe the law concerning that:

for the blood is the life :
which is the reason given for the prohibition of it, (See Gill on Leviticus 17:11),

and you may not eat the life with the flesh :
by which it seems that the meaning of the law was, that the blood might not be eaten in or with the flesh, but to be let out of it, or the fish not to be eaten raw, but dressed; for there were various laws about eating of blood, which are differently expressed.