SB 10.10.9

When the modes of passion and ignorance increase in human society, giving rise to unnecessary economic development, the result is that people become involved with wine, women and gambling. Then, being mad, they maintain big slaughterhouses or occasionally go on pleasure excursions to kill animals. Forgetting that however one may try to maintain the body, the body is subject to birth, death, old age and disease, such foolish rascals engage in sinful activities, one after another. Being duṣkṛtīs, they completely forget the existence of the supreme controller, who is sitting within the core of everyone’s heart (īśvaraḥ sarva-bhūtānāṁ hṛd-deśe ’rjuna tiṣṭhati). That supreme controller is observing every bit of one’s activity, and He rewards or punishes everyone by giving one a suitable body made by material nature (bhrāmayan sarva-bhūtāni yantrārūḍhāni māyayā). In this way, sinful persons automatically receive punishment in different types of bodies. The root cause of this punishment is that when one unnecessarily accumulates wealth, one becomes more and more degraded, not knowing that his wealth will be finished with his next birth.

na sādhu manye yata ātmano ’yam
asann api kleśada āsa dehaḥ
(Bhāg. 5.5.4)

Animal killing is prohibited. Every living being, of course, has to eat something (jīvo jīvasya jīvanam). But one should be taught what kind of food one should take. Therefore the Īśopaniṣad instructs, tena tyaktena bhuñjīthāḥ: one should eat whatever is allotted for human beings. Kṛṣṇa says in Bhagavad-gītā (9.26):

patraṁ puṣpaṁ phalaṁ toyaṁ
yo me bhaktyā prayacchati
tad ahaṁ bhakty-upahṛtam
aśnāmi prayatātmanaḥ
“If one offers Me with love and devotion a leaf, a flower, fruit or water, I will accept it.” A devotee, therefore, does not eat anything that would require slaughterhouses for poor animals. Rather, devotees take prasāda of Kṛṣṇa (tena tyaktena bhuñjīthāḥ). Kṛṣṇa recommends that one give Him patraṁ puṣpaṁ phalaṁ toyam — a leaf, a flower, fruit or water. Animal food is never recommended for human beings; instead, a human being is recommended to take prasāda, remnants of food left by Kṛṣṇa. Yajña-śiṣṭāśinaḥ santo mucyante sarva-kilbiṣaiḥ (Bg. 3.13). If one practices eating prasāda, even if there is some little sinful activity involved, one becomes free from the results of sinful acts.