SB 4.19.23

yāni rūpāṇi jagṛhe
 indro haya-jihīrṣayā
tāni pāpasya khaṇḍāni
 liṅgaṁ khaṇḍam ihocyate
Synonyms: 
yāni — all those which; rūpāṇi — forms; jagṛhe — accepted; indraḥ — the King of heaven; haya — the horse; jihīrṣayā — with a desire to steal; tāni — all those; pāpasya — of sinful activities; khaṇḍāni — signs; liṅgam — the symbol; khaṇḍam — the word khaṇḍa; iha — here; ucyate — is said.
Translation: 
Whatever different forms Indra assumed as a mendicant because of his desire to seize the horse were symbols of atheistic philosophy.
Purport: 

According to Vedic civilization, sannyāsa is one of the essential items in the program of the varṇāśrama institution. One should accept sannyāsa according to the paramparā system of the ācāryas. At the present moment, however, many so-called sannyāsīs or mendicants have no understanding of God consciousness. Such sannyāsa was introduced by Indra because of his jealousy of Mahārāja Pṛthu, and what he introduced is again appearing in the Age of Kali. Practically none of the sannyāsīs in this age are bona fide. No one can introduce any new system into the Vedic way of life; if one does so out of malice, he is to be known as a pāṣaṇḍī, or atheist. In the Vaiṣṇava Tantra it is said:

yas tu nārāyaṇaṁ devaṁ
 brahma-rudrādi-daivataiḥ
samatvenaiva vīkṣeta
 sa pāṣaṇḍī bhaved dhruvam

Although it is forbidden, there are many pāṣaṇḍīs who coin terms like daridra-nārāyaṇa and svāmi-nārāyaṇa, although not even such demigods as Brahmā and Śiva can be equal to Nārāyaṇa.