Sri Caitanya Caritamrta, Adi-lila, chapter 1, texts 44-46.
Translation by Srila A.C. Bhaktivedanta Swami Prabhupada: "Although I know my spiritual master as a servitor of Sri Caitanya, I know him also as prakasa, a plenary manifestation of the Lord. According to the deliberate opinion of all revealed scriptures, the spiritual master is non-different from Krsna, krsna-rupa. Lord Krsna, in the form of the spiritual master, delivers His devotees. One should know the acarya as Myself [Krsna], and never disrespect him in any way. One should not envy him, thinking him an ordinary man, for he is a representative of all the demigods."
Srila Narayana Maharaja: Those so-called gurus who think the acarya is like us - that he is an ordinary person with a material body and material senses, and maybe somewhat more intelligent than us - are most offensive. You should do pranama to them from very far away. Don't associate with and don't give any respect to such bogus gurus. And then siksa guru.
Text 47: "One should know the siksa-guru, instructing spiritual master, to be the personality of Krsna, krsna-svarupa. Lord Krsna manifests himself as the Supersoul and also as the greatest devotee of the Lord."
Srila Narayana Maharaja: Who is diksa-guru? Who is siksa-guru? The same qualifications will be there in both. For example, Srimad Bhagavatam is the best evidence, more so than the Vedas, more than the Upanisadas, more than Mahabharata, Hari-vamsa, the other Puranas, or any other grantha, scripture. It is amala pramana, spotless evidence. Tulsidasa has translated many of the verses of Srimad Bhagavatam in his Hindi Rama Carita Manasa. In writing his Ramayana, Valmiki also took all siddhanta from Srimad Bhagavatam. All bona fide gurus are in the same line. They are not against one another.
Scripture explains the qualifications of a real guru. Tad-vijnanartham sa gurum evabhigacchet, samit-pani srotriyam brahma-nistham.
["To understand these things properly, one must humbly approach, with firewood in hand, the spiritual master who is learned in the Vedas and firmly devoted to the Absolute Truth" (Mundaka Upanisad).]
Thus it has been enjoined herewith that in order to receive that transcendental knowledge, one must approach a transcendental guru. Therefore, if the Absolute Truth is one, about which we think there is no difference of opinion, the guru must also be one, he cannot be two. The Acaryadeva for whom we have assembled tonight to offer our humble homage is not the guru of a sectarian institution or one out of many differing exponents of the truth. On the contrary, he is the Jagad-guru, or the guru of all of us; the only difference is that some obey him wholeheartedly, while others do not obey him directly - Srila Prabhupada glorifying Srila Bhaktisiddhanta Sarasvati Thakur Prabhupada in Bombay, February 1936, on the occasion of Sri Vyasapuja
Srila Bhaktivedanta Narayana Gosvami Maharaja, lecture in Salt Spring Island, Canada, April 21, 2001