Question: If Jesus Christ was a jagad-guru and his instructions are capable of bringing us deliverance, why do we need a spiritual master?
Srila Bhaktisiddhanta Saraswati Prabhupada: We accept both the universal spiritual master and the initiating spiritual master. By accepting only the jagad-guru, we may face many anarthas. If at present we want to follow Christ's orders by accepting him as jagad-guru and we think we do not require an initiating spiritual master, we will certainly face doubt about how well we can follow Christ's orders. The Supreme Lord or universal jagad-guru delivers his instructions about the absolute truth only through the disciplic succession.
As I sit on the bank of the Ganga in Nabadwip, far from the Himalayas where the Ganga originates, and am able to touch her water here, the initiating spiritual master similarly brings the Ganga of pure devotional service, which emanates from the lord's lotus feet, and places it in my hand and on my head. Because I am an ordinary, powerless, poor person, I am not able to climb the Himalayas to touch her water there. Similarly, if the flow of the Ganga from the Himalayas is interrupted on the way, I would have to face the danger of accepting a polluted flow instead of the pure Ganga.
If the instructions Jesus Christ gave two thousand years ago do not come to us through disciplic succession, or if we have to sort them out from books, then perhaps we may create a blunder and accept a perversion of the truth taught in the name of Christianity. We may even come to accept something opposite from what he taught, thinking it his actual philosophy.
The initiating spiritual master is also jagad-guru because he is a manifestation of the original jagad-guru. Out of his causeless mercy he delivers the message of the original jagad-guru through the disciplic succession. He does not cheat or flatter the disciple, nor does he yearn for any material gain. He is simply a messenger of the absolute truth."
Source: Amrta Vani, p. 44, Touchstone Media, Mumbai, 2004