By His Divine Grace A. C. Bhaktivedānta Swami Prabhupāda
Śva-paco means candāla, one who eats dogs. He is considered the lowest. There are different kinds of meat-eaters. But in India, there were no cow-flesh-eaters. Some of them were eating hogs, even dogs. But no government will allow to eat the flesh of a cow. No, that is not allowed. If you want to eat flesh, you can eat hogs and dogs, and goats also. But you cannot touch a cow. This is the restriction. First of all, they should not be meat-eaters. But even if you are a staunch meat-eater, still you cannot touch the cow. You can eat some other animal.
So śva-pacah means the dog-eaters. In Korea, and some parts of the world, they eat dogs. Theysell dog flesh publicly. So in India also there is a class of meat-eaters. In Assam side, they eat dogs. So the dog-eaters are considered the lowest of mankind. Śva-pacah. Śva means dog and pacah means who cooks. Śva-pacah means candāla.
If a man from the śva-pacah or the candāla family becomes a Vaishnava (devotee of Krishna), strictly according to the orders, then he can become guru, but a brāhmana cannot become a guru if he’s not a Vaishnava. This is the stricture. Even if one is born in the family of a brāhmana, and he’s not only born, he’s even qualified – sat-karma-nipuno, nipuno means qualified – but still he cannot become a guru.
avaisnavo gurur na syād
vaisnavah śva-paco guruh
“A scholarly brahmana, expert in all subjects of Vedic knowledge, is unfit to become a spiritual master without being a Vaishnava, or expert in the science of Krishna consciousness. But a person born in a family of a lower caste can become a spiritual master if he is a Vaishnava, or Krishna conscious.”
[An excerpt from a lecture delivered on the Bhagavad-gita 1.40 in London on July 28, 1973]