CC Madhya 24.342

ei sabe viddhā-tyāga, aviddhā-karaṇa
akaraṇe doṣa, kaile bhaktira lambhana
Synonyms: 
ei sabe — all these things; viddhā-tyāga — to avoid viddha-ekādaśī or mixed Ekādaśī; aviddhā-karaṇa — performing the pure Ekādaśī; akaraṇe doṣa — the fault of not performing them; kaile — if done so; bhaktira lambhana — there will be discrepancies in devotional service.
Translation: 
“You should recommend the avoidance of mixed Ekādaśī and the performance of pure Ekādaśī. You should also describe the fault in not observing Ekādaśī. 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.