From holy vedas
Atharva Veda says:
(Atharva Veda 10.1.29)
Abstract meaning: It is definitely a great sin to kill innocents. Do not kill our cows, horses and people.
Atharva Veda 8.6.23
Abstract Meaning: We ought to destroy those who eat cooked as well as uncooked meat, meat involving destruction of males and females, fetuses and eggs.
(Atharva Veda 6.140.2)
Abstract meaning: You eat rice, barley, gram and sesame. These cereals are specifically meant for you. Do not kill those who are capable of being fathers and mothers
Yajur Veda 1.1
Abstract Meaning: O human! Animals are Aghnya – NOT TO BE KILLED. PROTECT THE ANIMALS.
From Manusmriti
5.51 He who approves, he who cuts, he who kills, he who buys and sells, he who cooks, he who serves and he who eats it are ‘slayers’—(51).
From mahabharat
स्वमांसं परमांसेन यो वर्धयितुमिइच्छति ।
नाति क्षुद्रतरस्त्स्मात्स नृशंसतरो नर: ।।
People who wish to increase their flesh by eating other's flesh are
the worst kind of creatures.
What will happen for meat eaters
"He who desires to augment his own flesh by eating the flesh of other creatures, lives in misery in whatever species he may take his [next] birth." (Mahabharata, Anu.115.47)