The words bhaktya kevalaya indicate that simply by executing devotional service one can become full of all knowledge. Krsna is the master of all knowledge (aisvaryasya samagrasya viryasya yasasah sriyah). The Lord is situated in everyones heart (isvarah sarva-bhutanam hrd-dese rjuna tisthati [Bg. 18.61]), and when the Lord is pleased with a devotee, the Lord instructs him. Only to the devotees, however, does the Lord give instructions by which to advance further and further in devotional service. To others, the nondevotees, the Lord gives instructions according to the manner of their surrender. The pure devotee is described by the words bhaktya kevalaya. Srila Visvanatha Cakravarti Thakura explains that bhaktya kevalaya means jnana-karmady-amisraya, unmixed with fruitive activities or speculative knowledge. Simply surrendering at the lotus feet is the cause of all a devotees enlightenment and awareness.