The Vedas enjoin: nayam atma pravacanena labhyo na medhaya na bahuna srutena. One cannot understand the Supreme Personality of Godhead simply by studying the Vedas and offering prayers. Only by the grace of the Supreme Lord can one understand Him. The process of understanding the Lord, therefore, is bhakti. Without bhakti, simply following the Vedic injunctions to understand the Absolute Truth will not be helpful at all. The process of bhakti is understood by the paramahamsa, one who has accepted the essence of everything. The results of bhakti are reserved for such a paramahamsa, and this stage cannot be obtained by any Vedic process other than devotional service. Other processes, such as jnana and yoga, can be successful only when mixed with bhakti. When we speak of jnana-yoga, karmayoga and dhyana-yoga the word yoga indicates bhakti. Bhakti-yoga, or buddhi-yoga, executed with intelligence and full knowledge, is the only successful method for going back home, back to Godhead. If one wants to be liberated from the pangs of material existence, he should take to devotional service for quick attainment of this goal.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Seventh Canto, Chapter 09 – Text 50