Tjyylli

I had posted the following in an answer but was urged to post it as a question.

I thought brahmins were not supposed to eat meat but I was reading MahAbhArata when I came across the following in sabhA parva.

भक्ष्यैर्मूलैैः फलैश्चैव मांसैर्वाराहहारिणैः ie by different types of foods like roots, fuit and pork and deer-meat

and again in

मांसैर्विबिधप्रकारैः खाद्यैश्चापि तथा नृप ie different types of meat and food (SabhA parva, 4th adhyaya, slokas 7 through 9)

which depict how dharma raja Yudhishtira fed the brahmanas before entering the palace of Indraprastha.

But it is a well known fact that Brahmanas shouldn't eat meat. Where does this come from?

Meat is considered a delicacy in the mahAbhArata.
But we know, for tradition, that we are not supposed to eat meat. Why did this tradition arise? If serving meat to brAhmanas was considered punya by vedavyasa, why do we consider it a sin?

Manu Smriti includes meat (prepared without spices) among Havi (i.e. food that are fit to be offered in Vedic sacrifices).

3.257. The food eaten by hermits in the forest, milk, Soma-juice, meat which is not prepared (with spices), and salt unprepared by art, are
called, on account of their nature, sacrificial food.

A Brahmin can meat under certain circumstances, and he has to only consume the meat that has been duly sprinkled with mantra-infused water.

5.27. One may eat meat when it has been sprinkled with water, while Mantras were recited, when Brahmanas desire (one’s doing it), when one
is engaged (in the performance of a rite) according to the law, and
when one’s life is in danger.

Only the meat that has been first offered in an animal sacrifice is however considered fit to be eaten.

4.27. A Brahmana, who keeps sacred fires, shall, if he desires to live long, not eat new grain or meat, without having offered the (Agrayana)
Ishti with new grain and an animal-(sacrifice).

Also, a Brahmin must not recite Vedas after he has consumed meat. So, if meat eating had been entirely prohibited for him, the following verse would not have been said:

4.112. While lying on a bed, while his feet are raised (on a bench), while he sits on his hams with a cloth tied round his knees, let him
not study, nor when he has eaten meat or food given by a person impure
on account of a birth or a death,

A Brahmin can not refuse eating meat in certain circumstances too, like in funeral ceremonies (Shraddhas).

And, a Brahmin becomes degraded if he chose not to eat meat, during the time when he is conducting a Vedic sacrifice.

See the following verses from Vyasa Smriti:

A Brahmana, engaged in the celebration of a religious sacrifice, becomes degraded by not taking meat.

A Kshatriya should eat the cooked flesh of a quarry after Jiaving
propitiated therewith the gods and his departed manes.

A Vaishya can take meat, lawfully obtained for money, after having
worshipped therewith his departed manes. (56, 57)

Eating non-sacrificial meat is of course never recommended in any scriptures.