Acts 15:20

"Speak to Aaron and his sons and to all the sons of Israel, and tell them: If anyone who is from among the sons of Israel or from among foreigners, who happens to be among you, eats any blood, I shall place my spirit over the spirit which shall have eaten the blood, and I shall abolish it from among the people, since the spirit of every flesh is its blood. To you I have also given the blood so that by it upon the altar there might be propitiations for your spirits, since the blood will make expiation for the spirit. Therefore, I have said to the sons of Israel: Every spirit among you shall not eat blood, and any foreigner among you shall not eat blood." You see, therefore, that this law regarding blood, given equally to both the sons of Israel and to foreigners, is even observed by us from among the Gentiles who believe in God through Jesus Christ. Scripture tends to call proselytes foreigners, as when it says, "The foreigner who is among you will rise up above you, while you descend below. He shall be your head, and you shall be his tail." Therefore, even the church of the Gentiles took in common with the people of Israel the law regarding blood, for that blessed council of the apostles, understanding that these things had been so written in the law, then ordered and decreed in writing the teachings for the Gentiles that they abstain not only from what had been sacrificed to idols and from fornication, but also from blood and from what had been suffocated. Now perhaps you will ask, "If Scripture was so clear with regard to blood, should it not also teach clearly about what has been suffocated, whether a law was given as common to the people of Israel and to foreigners, since the teachings of the apostles decree that Gentiles also observe this law?" Listen how observantly even this is guarded against in the laws of God: "If a man, any man," it says, "from the sons of Israel and from the foreigners among you, hunts a beast or a bird, let him pour out its blood and cover it with earth, for the spirit of every flesh is its blood."

"But the ways in which this garment may be spotted are these: If any one withdraw from God the Father and Creator of all, receiving another teacher besides Christ, who alone is the faithful and true Prophet, and who has sent us twelve apostles to preach the word; if any one think otherwise than worthily of the substance of the Godhead, which excels all things;— these are the things which even fatally pollute the garment of baptism. But the things which pollute it in actions are these: murders, adulteries, hatreds, avarice, evil ambition. And the things which pollute at once the soul and the body are these: to partake of the table of demons, that is, to taste things sacrificed, or blood, or a carcass which is strangled, and if there be anything else which has been offered to demons. Be this therefore the first step to you of three; which step brings forth thirty commands, and the second sixty, and the third a hundred, as we shall expound more fully to you at another time."

"But that we write unto them, that they abstain from pollutions of idols, and from fornication" - and yet they often insisted upon these points in discoursing to them - but, that he may seem also to honor the Law he mentions these also, speaking however not as from Moses but from the Apostles, and to make the commandments many, he has divided the one into two saying, "and from things strangled, and from blood." For these, although relating to the body, were necessary to be observed, because these things caused great evils. "From things strangled," it says, "and from blood." Here it prohibits murder.

And from things strangled, and blood, that is, from shedding blood or eating with blood. These indeed were allowed for those coming from a Gentile life, as the rudiments of the faith and the ingrained habit of Gentilism, but lest they should think that the same sufficed even for the more perfect, he diligently added and said...

To abstain from the pollutions of idols, and fornication, and that which is strangled, and blood. He speaks of that which is strangled as carrion, about which Ezekiel writes: "The priests shall not eat anything that is dead of itself or torn by beasts, whether it be from birds or from cattle" (Ezek. XLIV). Jerome explains this: "And according to the literal sense, says he, this pertains to the whole chosen royal and priestly race, which properly refers to Christians, who are anointed with spiritual oil, about which it is written: 'God, your God, has anointed you with the oil of gladness above your companions.' These precepts apply, that they do not eat dead flesh, whether from birds or from cattle, whose blood has by no means been shed, which in the Acts of the Apostles is called strangled; and the epistle of the Apostles from Jerusalem warns that these things should necessarily be observed; and what is taken by a beast, because this too is similarly strangled; and it condemns priests who, with gluttonous greed, keep these things from thrushes, fig-peckers, dormice, and the like."

These precautions, although they concern sensible things, are nevertheless necessary. Since these things were the cause of many evils, it was primarily from them that James restrained the believers.