The Vedic mantra are so powerful that that was a test how a dead animal can get, regain new body. An old animal is sacrificed and it gets a new youthful life. That was the test. It was not meant for killing. Don't misunderstand that sacrifice. But that is mentioned in the Vedas. So people misused that sacrifice means... That sacrifice... They wanted to give evidence from Vedas, "So here is... Animal sacrifice is mentioned in the Vedas. Why we shall stop?" So Lord Buddha started his movement, completely stopping this animal sacrifice. But he knew that "These foolish men will come and give me evidence that 'Here in the Vedas animal sacrifice is recommended. Why you are preaching? Why you are preaching stoppage of animal killing?' " Therefore he completely rejected Vedas. He said that "I don't accept Vedas."
That is stated in a very nice verse about Lord Buddha by a Vaiṣṇava poet.
- nindasi yajña-vidher ahaha śruti-jātaṁ
- sadaya-hṛdaya darśita-paśu-ghātam
- keśava dhṛta-buddha-śarīra jaya jagadīśa hare
It is very nicely composed. The idea is that the poet is praying Lord Buddha. And Lord Buddha is also mentioned in Bhāgavatam as incarnation of Kṛṣṇa. So he is praying Lord Buddha, "My dear Lord, you have assumed now the buddha-śarīra, body, just to, by taking compassion on the poor animals, and therefore you are also deprecating the animal sacrifices recommended in the Vedas."
So because Lord Buddha did not accept... He had to do that because his mission was to stop animal sacrifice and animal killing. "Now if these foolish persons, without knowing the Vedic purpose, if they present, 'Oh, here it is recommended in the Vedas,' then there will be disturbance." So he had to discard, he had to go out of the Vedic rules and regulation, and he preached his own philosophy.