From the very beginning of His childhood life Śrī Caitanya Mahāprabhu introduced the system of observing a fast on the Ekādaśī day. In the Bhakti-sandarbha, by Śrīla Jīva Gosvāmī, there is a quotation from the Skanda Purāṇa admonishing that a person who eats grains on Ekādaśī becomes a murderer of his mother, father, brother and spiritual master, and even if he is elevated to a Vaikuṇṭha planet, he falls down. On Ekādaśī, everything is cooked for Viṣṇu, including regular grains and dahi, but it is enjoined that a Vaiṣṇava should not even take viṣṇu-prasāda on Ekādaśī. It is said that a Vaiṣṇava does not accept anything eatable that is not offered to Lord Viṣṇu, but on Ekādaśī a Vaiṣṇava should not touch even mahā-prasāda offered to Viṣṇu, although such prasāda may be kept for being eaten the next day. It is strictly forbidden for one to accept any kind of grain on Ekādaśī, even if it is offered to Lord Viṣṇu.
Devotional service in Kṛṣṇa consciousness cannot be performed blindly due to material emotion or mental concoction. It is specifically mentioned here that one has to perform devotional service in full knowledge by visualizing the Absolute Truth. We can understand about the Absolute Truth by evolving transcendental knowledge, and the result of such transcendental knowledge will be manifested by renunciation. That renunciation is not temporary or artificial, but is very strong. It is said that development of Kṛṣṇa consciousness is exhibited by proportionate material detachment, or vairāgya. If one does not separate himself from material enjoyment, it is to be understood that he is not advancing in Kṛṣṇa consciousness. Renunciation in Kṛṣṇa consciousness is so strong that it cannot be deviated by any attractive illusion. One has to perform devotional service in full tapasya, austerity. One should fast on the two Ekādaśī days, which fall on the eleventh day of the waxing and waning moon, and on the birthdays of Lord Kṛṣṇa, Lord Rāma and Caitanya Mahāprabhu. There are many such fasting days. Yogena means “by controlling the senses and mind.” Yoga indriya-saṁyamaḥ. Yogena implies that one is seriously absorbed in the self and is able, by development of knowledge, to understand his constitutional position in relationship with the Superself. In this way one becomes fixed in devotional service, and his faith cannot be shaken by any material allurement.