Srimad-Bhagavatam: Canto 1 - Chapter 1 - Verse 52


यथा पङ्केन पङ्काम्भ: सुरया वा सुराकृतम् ।भूतहत्यां तथैवैकां न यज्ञैर्मार्ष्टुमर्हति ॥ ५२ ॥


yathā paṅkena paṅkāmbhaḥsurayā vā surākṛtambhūta-hatyāṁ tathaivaikāṁna yajñair mārṣṭum arhati


As it is not possible to filter muddy water through mud, or purify a wine-stained pot with wine, it is not possible to counteract the killing of men by sacrificing animals.


Aśvamedha-yajñas or gomedha-yajñas, sacrifices in which a horse or a bull is sacrificed, were not, of course, for the purpose of killing the animals. Lord Caitanya said that such animals sacrificed on the altar of yajña were rejuvenated and a new life was given to them. It was just to prove the efficacy of the hymns of the Vedas. By recitation of the hymns of the Vedas in the proper way, certainly the performer gets relief from the reactions of sins, but in case of such sacrifices improperly done under inexpert management, surely one has to become responsible for animal sacrifice. In this age of quarrel and hypocrisy there is no possibility of performing the yajñas perfectly for want of expert brāhmaṇas who are able to conduct such yajñas. Mahārāja Yudhiṣṭhira therefore gives a hint to performing sacrifices in the Age of Kali. In the Kali-yuga the only sacrifice recommended is the performance of hari-nāma-yajña inaugurated by Lord Śrī Caitanya Mahāprabhu. But one should not indulge in animal killing and counteract it by performing the hari-nāma-yajña. Those who are devotees of the Lord never kill an animal for self-interest, and (as the Lord ordered Arjuna) they do not refrain from performing the duty of a kṣatriya. The whole purpose, therefore, is served when everything is done for the will of the Lord. This is possible only for the devotees.