In Vinaya, there is this rule (copied from Buddhist Monastic Code II):
"One should not knowingly consume meat killed on purpose (for a bhikkhu). Whoever should consume it: an offense of wrong doing. I allow fish and meat that is pure in three respects: One has not seen, heard, or suspected (that it was killed on purpose for a bhikkhu)." — Mv.VI.31.14
How should we interpret "heard"? I can think of some possibilities:
- Heard from someone that it was killed for me, i.e., someone told me that it was killed for me.
- Heard the sound of killing, e.g. sound of the animal or action of killing
- Both of the above.