Guru is the quintessence of Devotion
Without the compassion of Guru, a devotee cannot acquire (divine) knowledge. The Guru is the manifested (embodied) Deity of a devotee from many lives before. The devotee claims “l offer my devotion to the Guru”. However, in reality the Guru is the very basis of devotion (of the devotee). In order to attract the devotee, He (the Guru) awakens (the feeling of) devotion in his heart. The Gurudev creates spiritual emotion in the devotee and Himself becomes the receiver of it.
Devotion won’t awaken in heart without the kindness of the Guru nor can one have knowledge or (capability) to practice righteousness.
When Guru’s compassion dawns, the sinful propensities (of the devotee) gradually reduces. When conscience awakens within, the devotee realizes the difference between the real and the unreal (things of life). The Guru shows the internal and external paths to get emancipation. As the devotee travels along the path (prescribed by the Guru), he gradually evolves spiritually.
When the power of the Guru permeates (the inner self of the devotee), noble thoughts awaken in the devotee’s mind. His thoughts become full of love and his deeds become pious. When the devotee concentrates on the Guru, he becomes oblivious of himself.
Source: Shri Guru Bhagavat, Vol.2 by Dr. C B Satpathy