Sad-dharma, or duty performed for going back to Godhead and thus becoming His unalloyed devotee, is the only pious activity; all others may pretend to be pious, but actually they are not. It is for this reason only that the Lord advises in the Bhagavad-gītā that one give up all so-called religious activities and completely engage in the devotional service of the Lord to become free from all anxieties due to the dangerous life of material existence.
-Shrimad Bhagavatam Canto 2 Chapter 10 Verse 4, Translation and Purport

एतावानेव लोकेऽस्मिन् पुंसां धर्म: पर: स्मृत: ।
भक्तियोगो भगवति तन्नामग्रहणादिभि: ॥ २२ ॥
Devotional service, beginning with the chanting of the holy name of the Lord, is the ultimate religious principle for the living entity in human society.
-Shrimad Bhagvatam Canto 6 Chapter 3 Verse 22