Sri Guru plants the seed of spiritual perfection through harinama and diksa-mantras. However, without repeated watering in the form of hearing hari-katha directly from the lotus lips of a sadhu (a saintly devotee), combined with a mood of rendering favourable service, nothing can grow or mature into perfection. A sadhu may recite rasika, sublime slokas, which may be difficult for us conditioned souls to fully understand. Yet these slokas are likened to transcendental seeds that will (for the faithful hearer), flourish one day into fully blossomed spiritual realizations.
Slokamritam - The Book - Śrīla Gurudeva