First of all kill the guru. That is called guru-mara-vidya. Guru advised that you take food in goodness, sattvika. So he first of all advised that don't take fish, just like we are advising, meat, eggs, don't take. Then they thought that "The cow is very pure. Cow is very pure, so let us eat cow, sattvika."

So when Guru Maharaja inquired that "You have given up everything bad?" "Yes, now we are eating cow." "What?" "No, it is sattvika." "No, no, no, no, no. You cannot eat even." Then they thought, "Then what we shall eat? Guru Maharaja is sattvika, most sattvika. So let us eat him." [laughter] So it is called guru-mara-vidya: "For sattvika eating, let us eat Guru Maharaja." This is intelligence. "Why so much botheration seeking here and there? The Guru Maharaja is there."

Srila Prabhupada; Morning Walk — May 21, 1975, Melbourne