When a pure devotee or spiritual master speak, what he says should be accepted as having been directly spoken by the Supreme Personality of Godhead in the Parampara System. — Sri Caitanya Caritamrita, Antya Lila, 05.71.
The spiritual master is the mercy representative of the Lord.
Srimad Bhagavatam 1.7.22,
Out of many millions of wandering living entities, one who is very fortunate gets an opportunity to associate with a bonafide spiritual master by the grace of Krishna. By the mercy of both Krishna and the spiritual masters, such a person receives the seed of the creeper of devotional service.
If we take shelter of the lotus feet of the spiritual master, we can become free from illusion, fear and distress. If we wholeheartedly beg for his mercy without any deceit then the spiritual master bestows all auspiciousness upon us.