Bhagavad-gita As It Is
BG Chapters 1 - 6
Birth in a family of yogīs or transcendentalists—those with great wisdom—is praised herein because the child born in such a family receives a spiritual impetus from the very beginning of his life. It is especially the case in the ācārya or gosvāmī families. Such families are very learned and devoted by tradition and training, and thus they become spiritual masters. In India there are many such ācārya families, but they have now degenerated due to insufficient education and training. By the grace of the Lord, there are still families that foster transcendentalists generation after generation. It is certainly very fortunate to take birth in such families. Fortunately, both our spiritual master, Oṁ Viṣṇupāda Śrī Śrīmad Bhaktisiddhānta Sarasvatī Gosvāmī Mahārāja, and our humble self had the opportunity to take birth in such families, by the grace of the Lord, and both of us were trained in the devotional service of the Lord from the very beginning of our lives.
SB Canto 2
In other words, the cleansing of the polluted heart by other methods (like the culture of empiric knowledge or mystic gymnastics) can simply cleanse one's own heart, but devotional service to the Lord is so powerful that it can cleanse the hearts of the people in general, by the devotional service of the pure, empowered devotee. A true representative of the Lord like Nārada, Śukadeva Gosvāmī, Lord Caitanya, the six Gosvāmīs and later Śrīla Bhaktivinoda Ṭhākura and Śrīmad Bhaktisiddhānta Sarasvatī Ṭhākura, etc., can deliver all people by their empowered devotional service.
By sincere efforts to hear Śrīmad-Bhāgavatam one realizes his constitutional relationship with the Lord in the transcendental humor of servitude, friendship, paternal affection or conjugal love, and by such self-realization one becomes situated at once in the transcendental loving service of the Lord. Not only were all the pure devotees like Nārada self-realized souls, but they were engaged in preaching work automatically by spiritual impetus, and thus they delivered many poor souls entangled in the material modes. They became so powerful because they sincerely followed the Bhāgavatam principles by regular hearing and worshiping. By such actions the accumulated material lusts, etc., become cleansed by the personal endeavor of the Lord within the heart. The Lord is always within the heart of the living being, but He becomes manifested by one's devotional service.