SB 4.11.10

nāyaṁ mārgo hi sādhūnāṁ
 hṛṣīkeśānuvartinām
yad ātmānaṁ parāg gṛhya
 paśuvad bhūta-vaiśasam
Synonyms: 
na — never; ayam — this; mārgaḥ — path; hi — certainly; sādhūnām — of honest persons; hṛṣīkeśa — of the Supreme Personality of Godhead; anuvartinām — following the path; yat — which; ātmānam — self; parāk — the body; gṛhya — thinking to be; paśu-vat — like animals; bhūta — of living entities; vaiśasam — killing.
Translation: 
One should not accept the body as the self and thus, like the animals, kill the bodies of others. This is especially forbidden by saintly persons, who follow the path of devotional service to the Supreme Personality of Godhead.
Purport: 

The words sādhūnāṁ hṛṣīkeśānuvartinām are very significant. Sādhu means “a saintly person.” But who is a saintly person? A saintly person is he who follows the path of rendering service unto the Supreme Personality of Godhead, Hṛṣīkeśa. In the Nārada-pañcarātra it is said, hṛṣīkeṇa hṛṣīkeśa-sevanaṁ bhaktir ucyate: the process of rendering favorable service to the Supreme Personality of Godhead with one’s senses is called bhakti, or devotional service. Therefore, why should a person who is already engaged in the service of the Lord engage himself in personal sense gratification? Dhruva Mahārāja is advised here by Lord Manu that since he is a pure servitor of the Lord, why should he unnecessarily engage, like the animals, in the bodily concept of life? An animal thinks that the body of another animal is his food; therefore, in the bodily concept of life, one animal attacks another. A human being, especially one who is a devotee of the Lord, should not act like this. A sādhu, a saintly devotee, is not supposed to kill animals unnecessarily.