“The seed of devotional service fructifies and becomes a transcendental creeper. Finally it reaches the lotus feet of the Lord in the spiritual sky. This seed is obtained by the mercy of the Lord and the guru. By the Lord's mercy one gets the association of a bona fide guru, and by the mercy of the guru, one gets a chance to render devotional service. Devotional service, the science of bhakti-yoga, carries one from this material world to the spiritual world.” (Shrila Prabhupada, Chaitanya Charitamrita, Madhya 13.18 Purport)