首楞嚴義疏注經 8.521

8.521

汝負他財，他欠汝力，今既酬償，償足自止，世養牛馬是此類也。如故殺彼，食其身肉，斯則翻成殺業，身身相取，命命相酬，以人食羊，羊死為人，互來相責，無有休止。以諸業中殺命最重，不值佛出，修奢摩他，必不能息。

If you owed another wealth, and they owed you labor, now that compensation has been made, when it is sufficient it naturally ceases; rearing oxen and horses in the world belongs to this kind. But if you deliberately killed them and ate their flesh, this turns into killing karma: body takes from body, life repays life; humans eat sheep, and the dead sheep becomes a human, returning mutually to exact retribution without cessation. Because among all karmas killing life is the gravest, if one does not encounter a Buddha appearing in the world and cultivate śamatha, it can never cease.