A.C. Bhaktivedanta Swami Prabhupada
It is not possible for a conditioned soul to directly meet Krishna – the Supreme Personality of Godhead, but if one becomes a sincere devotee and seriously engages in devotional service, Lord Krishna sends an instructing spiritual master to show him favour and invoke his dormant propensity for serving the Supreme. The preceptor appears before the external senses of the fortunate conditioned soul and at the same time the devotee is guided from within by the Caitya-Guru – Krishna who is seated as the spiritual master within the heart of the living entity.
A.C. Bhaktivedanta Swami Prabhupada
When a pure devotee or spiritual master speaks, what he says should be accepted as having been directly spoken by the Supreme Personality of Godhead in the Parampara system.
A.C. Bhaktivedanta Swami Prabhupada
Our first duty is to satisfy the spiritual master, who can arrange for the Lord’s mercy. A common man must first begin to serve the spiritual master or the devotee. Then, through the mercy of the devotee, the Lord will be satisfied. Unless one receives the dust of a devotee’s lotus feet on one’s head, there is no possibility of advancement. Unless one approaches a pure devotee, he cannot understand the Supreme Personality of Godhead.
A.C. Bhaktivedanta Swami Prabhupada
If one is not actually connected with a bona fide disciplic succession, whatever mantaras he chants will not bring the desired result.