You can't eat blood, or stuff with blood in it. (Cooked pig blood is a popular cuisine choice in Jakarta.) Actually what is the meaning of not eating stuff with blood in it? Is it because you can't eat things when they are alive?
To be more exact here
Are we prohibited to eat
As with all mitzvos, there are various reasons suggested.
The Torah says in various ways כי דם הוא הנפש (Vayikra 17:11, Vayikra 17:14, Devarim 12:23), the soul is connected to the blood of a living creature.
The Sefer HaChinuch (#148) says the reason is the same as he gave for the prohibition against treifos (#73) and forbidden fats (#147) (that they are physically harmful to the body, and we need healthy bodies to serve Hashem).
However, he adds:
מלבד רע מזגו, שהוא רע המזג, יהיה באכילתו קצת קנין במדת אכזריות, שיבלע האדם מבעלי-החיים שכמותו בגוף, אותו הדבר שבהם שהחיות ממש תלוי עליו, ונפשם נקשרת בו.
Besides its evil nature (because [blood] is evil in nature), there will be in eating it a slight acquisition of the trait of cruelty. [Why?] This is from swallowing from living animals that which is similar to his own body, meaning that which his lifesource is dependent on and soul is bound to.
He also brings the explanation of the Ramban (Vayikra 17:11) that everything we eat is converted into the body. If a person eats blood, there will be עובי וגסות הרוח (I'd translate that as haughtiness, although I'm not sure) which enters the soul of a person. This is because the נפש (which is in the blood) of animals is עבה וגסה. He also agrees with the Chinuch that it is not fitting for a נפש to eat a נפש
As with all mitzvos, there are various reasons suggested Except for the Parah Adumah. :P
– ezra
Jun 29 '17 at 22:05
The Torah basically tells us the reason. Leviticus 17:10-12 says:
וְאִישׁ אִישׁ מִבֵּית יִשְׂרָאֵל, וּמִן-הַגֵּר הַגָּר בְּתוֹכָם, אֲשֶׁר יֹאכַל, כָּל-דָּם--וְנָתַתִּי פָנַי, בַּנֶּפֶשׁ הָאֹכֶלֶת אֶת-הַדָּם, וְהִכְרַתִּי אֹתָהּ, מִקֶּרֶב עַמָּהּ. כִּי נֶפֶשׁ הַבָּשָׂר, בַּדָּם הִוא, וַאֲנִי נְתַתִּיו לָכֶם עַל-הַמִּזְבֵּחַ, לְכַפֵּר עַל-נַפְשֹׁתֵיכֶם: כִּי-הַדָּם הוּא, בַּנֶּפֶשׁ יְכַפֵּר. עַל-כֵּן אָמַרְתִּי לִבְנֵי יִשְׂרָאֵל, כָּל-נֶפֶשׁ מִכֶּם לֹא-תֹאכַל דָּם; וְהַגֵּר הַגָּר בְּתוֹכְכֶם, לֹא-יֹאכַל דָּם.
And whatsoever man there be of the house of Israel, or of the strangers that sojourn among them, that eateth any manner of blood, I will set My face against that soul that eateth blood, and will cut him off from among his people. For the life of the flesh is in the blood; and I have given it to you upon the altar to make atonement for your souls; for it is the blood that maketh atonement by reason of the life. Therefore I said unto the children of Israel: No soul of you shall eat blood, neither shall any stranger that sojourneth among you eat blood.
In other words, the blood of an animal is designated for ritual purposes, so we shouldn't eat it. We see the same phenomenon by the prohibition on eating suet which is also designated for ritual use in the Temple, as earlier in Leviticus 7:23-26 it says:
דַּבֵּר אֶל-בְּנֵי יִשְׂרָאֵל, לֵאמֹר: כָּל-חֵלֶב שׁוֹר וְכֶשֶׂב, וָעֵז--לֹא תֹאכֵלוּ. וְחֵלֶב נְבֵלָה וְחֵלֶב טְרֵפָה, יֵעָשֶׂה לְכָל-מְלָאכָה; וְאָכֹל, לֹא תֹאכְלֻהוּ. כִּי, כָּל-אֹכֵל חֵלֶב, מִן-הַבְּהֵמָה, אֲשֶׁר יַקְרִיב מִמֶּנָּה אִשֶּׁה לַיהוָה--וְנִכְרְתָה הַנֶּפֶשׁ הָאֹכֶלֶת, מֵעַמֶּיהָ. וְכָל-דָּם לֹא תֹאכְלוּ, בְּכֹל מוֹשְׁבֹתֵיכֶם, לָעוֹף, וְלַבְּהֵמָה. כָּל-נֶפֶשׁ, אֲשֶׁר-תֹּאכַל כָּל-דָּם--וְנִכְרְתָה הַנֶּפֶשׁ הַהִוא, מֵעַמֶּיהָ.
Speak unto the children of Israel, saying: Ye shall eat no fat, of ox, or sheep, or goat. And the fat of that which dieth of itself, and the fat of that which is torn of beasts, may be used for any other service; but ye shall in no wise eat of it. For whosoever eateth the fat of the beast, of which men present an offering made by fire unto the LORD, even the soul that eateth it shall be cut off from his people. And ye shall eat no manner of blood, whether it be of fowl or of beast, in any of your dwellings. Whosoever it be that eateth any blood, that soul shall be cut off from his people.
Note the prohibition on blood is repeated there in the same section.
The remaining question is why is blood prohibited in all animals and birds while suet is only prohibited in animals offered as sacrifices in the Temple? The simple answer is suet only serves a ritual role in those animals, while the blood serves a ritual role (via slaughtering) in all animals and birds. (One could even argue that what we think of as ordinary slaughtering outside the Temple is really a type of quasi-Korban, cf. Deuteronomy 14.)
Your question is very unclear, but since the others took it as a general question about the purpose of the prohibition of eating blood, i will provide the relevant sources.
Ramban: Blood is the force of life and the soul of the living, it belongs to god alone, that is why a human being should not eat blood: one who possesses a soul shall not eat a soul (ואין לבעל נפש שיאכל נפש). He adds that blood may be prohibited because it is reserved for the altar (or god), and is similar to the prohibition of the fats (according to this understanding, the blood of the wild animals are prohibited so that we don't come to eat the blood of the sacrificial animals. Apparently the Ramban wasn't comfortable with this reason alone so he added another. Ramban vayikra 17:11-12).
Rambam: the pagans used to eat blood in order to connect to the demons believing that it enables them to see the future, that is why the Torah prohibited it (Rambam Moreh 3, 46).
Chinuch: because the blood can physically harm the person that consumes it. The Ramban explains it similarly: the food that a person eats becomes part of him, if he eats the blood of the animal (which is the living force of the animal) he will become coarse/crude like an animal, and the blood will produce a thickness/coarseness within him (עובי וגסות Chinuch 148).
C. M. Carmichael: Blood symbolizes life, the flesh symbolizes death (since it rots and disintegrates after death), That's why the Israelite's shall not mix them together in their food. The blood prohibition comes to emphasize the separation between life and death, and that they should choose life over death. In a similar vein he explains the prohibition of eating the kid and its mother's milk, and many others. The concept of choosing life over death is clearly expressed in Devarim 30:19. This may be the motive behind the prohibition of eating blood since it is mixing life and death together and blurring the distinction between them. (C. M. Carmichael, “On Separating Life and Death: An Explanation of Some Biblical Laws”, HTR 69 (1976), pp. 1-7).
