Prabhupada Letters :: 1968.

"That is the secret of Krishna Consciousness. The Spiritual Master must be bona fide representative of Krishna, and the disciple must agree to abide by His orders. This is the simple method of spiritual advancement."

Prabhupada Letters :: 1972.

"Krishna's plan becomes very easy for us when we follow Krishna's orders, otherwise, we are following Maya's plan. Following Krishna's orders means chanting daily 16 rounds, the four rules, rising early, like that."