Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 30

Sanskrit:

वेदवादरतो न स्यान्न पाषण्डी न हैतुक: ।शुष्कवादविवादे न कञ्चित् पक्षं समाश्रयेत् ॥ ३० ॥

ITRANS:

veda-vāda-rato na syānna pāṣaṇḍī na haitukaḥśuṣka-vāda-vivāde nakañcit pakṣaṁ samāśrayet

Translation:

A devotee should never engage in the fruitive rituals mentioned in the karma-kāṇḍa section of the Vedas, nor should he become atheistic, acting or speaking in opposition to Vedic injunctions. Similarly, he should never speak like a mere logician or skeptic or take any side whatsoever in useless arguments.

Purport:

Although a paramahaṁsa devotee conceals his exalted position, certain activities are forbidden even for one trying to conceal himself. Śrīla Viśvanātha Cakravartī Ṭhākura explains that in the name of concealment one should not become a ghost. The word pāsaṇḍa refers to atheistic philosophies opposing the Vedas, such as Buddhism, and haituka refers to those who accept only that which can be demonstrated by mundane logic or experimentation. Since the whole purpose of the Vedas is to understand that which is beyond material experience, a skeptic’s so-called logic is irrelevant to spiritual progress. Śrīla Jīva Gosvāmī warns us in this regard that a devotee should not read atheistic literature, even with the purpose of refining arguments against atheism. Such literature should be entirely avoided. The above-mentioned prohibited activities are so detrimental to the advancement of Kṛṣṇa consciousness that they should not be adopted even as a superficial show.