Because a devotee means one who has dedicated—I have already explained the other day—dedicated his body, mind and words for Kṛṣṇa. That is the test of devotee, whether he has engaged these three things to the service of the Lord. Then he is devotee. Body . . . because our all activities are based on these three principles. With mind we plan: thinking, feeling and willing. And willing is given practical shape by the bodily work, or words, by speaking.
So this is the test of a devotee. Prahlāda Mahārāja says he may be born in a family of the dog-eaters, but because he has engaged his body, mind and words for Kṛṣṇa, for service of Kṛṣṇa, then he is better, he is superior, he is in superior position than the so-called brahmin with all good qualifications but without any devotional spirit.
And why he is preferred? Prāṇaṁ punāti sa kulaṁ. This man, this śvapacaṁ, or the man born in the family of caṇḍāla, he is able to deliver his whole dynasty. Whole dynasty, sa kulaṁ. This very word is used here, prāṇaṁ punāti. He personally becomes purified. There is no doubt about it. Prāṇaṁ. His life is perfect, punāti. Punāti means purified, and sa kulaṁ, sa kulaṁ means along with his family members.
He is not only personally becoming purified, but his parents, his parents' father, his father, his brother, his . . . sa kulaṁ. Kulaṁ, kulaṁ means the whole family. Sa kulaṁ punāti. Aravinda-nābha pādāravinda-vimukhāt śvapacaṁ (SB 7.9.10). What kind of fifth-class man? He is not fifth-class man. He may be born in a fifth-class family, but he is not fifth class.
Just like Prahlāda Mahārāja. Prahlāda Mahārāja, directly his father is a great demon, but he is not demon. It does not mean that a person born of low family is also low. This is not the verdict of Vedas. They . . . vedic culture was lost, or put into difficulty, simply for this reason, when the Vedic followers in India, they made these classification of brahmin, kṣatriya, as hereditary.