dina-kṛtya, pakṣa-kṛtya, ekādaśy-ādi-vivaraṇa
"You should describe the ritualistic duties of every day, and you should describe the fortnightly duties-especially observing Ekādaśī fast, which comes every fortnight. You should also describe the duties of every month, especially the observance of ceremonies like Janmāṣṭamī, Rāma-navamī and Nṛsiṁha-caturdaśī.
Śrī Caitanya-caritāmṛta Madhya 24.340
ei sabe viddhā-tyāga, aviddhā-karaṇa
akaraṇe doṣa, kaile bhaktira lambhana
"You should recommend the avoidance of mixed Ekādaśī and the performance of pure Ekādaśī. You should also describe the fault in not observing this. One should be very careful as far as these items are concerned. If one is not careful, one will be negligent in executing devotional service.
Śrī Caitanya-caritāmṛta Madhya 24.342