So, parāvare brahmaṇi dharmato vrataiḥ. So one should execute Kṛṣṇa consciousness, dharmataḥ, in right path, and vrataiḥ. Bhajante māṁ dṛḍha-vratāḥ. Just like today, ekādaśī-vrata. Vrataiḥ. This ekādaśī-vrata is required. Just see. Here it is that "You have performed all the vratas." The purpose of ekādaśī-vrata is that today we should not eat much usual food, grains. The actual prescription is fasting. Nirjala-ekādaśī. Nirjala means there are many devotees who does not take even water. Water, drinking water, according to śāstra, it is taking food... It is drinking of food or no food. We can take both ways. So sometimes drinking of water is excused as upavāsa also. But there are many devotees who even..., drink even a drop of water. Whole day and night they fast and observe ekādaśī-vrata. And the night is called harivāsara. Harivāsara means the whole night they would chant Hare Kṛṣṇa, Hare Kṛṣṇa, Kṛṣṇa Kṛṣṇa, Hare Hare/ Hare Rāma, Hare Rāma... This is called vrata. Dṛḍha-vrata. Dṛḍha-vrata.
Śrīmad-Bhāgavatam 1.5.1-8 -- New Vrindaban, May 23, 1969
"A person who is actually a devotee of Kṛṣṇa does not care about so-called public opinion and Vedic or philosophical literatures. Prahlāda Mahārāja, who is such a devotee, always defied the false instructions of his father and the so-called teachers who were appointed to teach him. Instead, he simply followed the instructions of Nārada Muni, his guru, and thus he always remained a stalwart devotee. This is the nature of an intelligent devotee."
Śrīla Prabhupāda, Śrīmad-Bhāgavatam 7.13.45 Purport