The life of man is in the blood. We cannot live without blood. It is scared to life itself. The Bible’s first prohibition against consuming blood comes in Genesis 9:2-4, where God tells Noah, "Everything that lives and moves about will be food for you. Just as I gave you the green plants, I now give you everything. But you must not eat meat that has its lifeblood still in it." This prohibition was most likely a ban on eating raw blood (i.e., uncooked meat). For the first time, animals were an allowable food source, and God was making sure that Noah did not eat them raw. A Jewish Targum comments on this verse: "But the flesh which is torn from a living beast at the time that its life is in it, or which is torn from a beast while it is slain, before all its breath is gone out, ye shall not eat."
Later, the prohibition of Genesis 9:4 is iterated in the Law of Moses. And later Peter received the vision about prohibited animals coming down and he was told to eat them and he refused. But God said what He calls clean is clean. Christians are allowed to eat anything as long as it doesn’t cause a weaker brother or sister to doubt.
Why is the blood so important? For our salvation it is vital. We shall see why...