Madhya Lila Chapter 24 Verse 251
This is another authoritative statement made by the great sage Narada. Those who kill animals and give them unnecessary pain--as people do in slaughterhouses--will be killed in a similar way in the next life and in many lives to come................
kadarthiya tumi yata marila jivere
tara taiche toma maribe janma-janmantare"
TRANSLATION
"Narada Muni continued, `All the animals that you have killed and given unnecessary pain will kill you one after the other in your next life ad in life after life.'