When good fortune awakens in our life and we receive the causeless mercy of the Lord, only then we get the opportunity to have the darshan (audience) of a pure devotee. We find descriptions of the characteristics of pure devotees in the Vedas, Puranas, and other scriptures. However, the Founder-Acharya of Sri Chaitanya Gaudiya Math, the most revered Tridandi Swami 108 Srimad Bhakti Dayita Madhava Goswami Maharaj Ji(param guruji), demonstrated through his life and pastimes what a pure Vaishnava truly is.

Once upon a time, Guruji, His divine grace Srila Bhakti Ballabh Tirtha Goswami Maharaj Ji — and Mangal Nilay Prabhu were discussing a principle from a scripture.

Mangal Nilay Prabhu was a highly learned scholar and deeply knowledgeable in the scriptures. During their discussion, a slight disagreement arose between the two.

Hearing of this, Param Gurudeva (Srila Bhakti Dayita Madhav Goswami Maharaj) personally came to their room.

Param Gurudeva said to Guruji : "Tirtha Maharaj, Mangal Nilay Prabhu is a great scholar, so you should not engage in arguments with him."
After that he said to Mangal Nilay Prabhu: "Mangal Prabhu, Tirtha Maharaj is a great Vaishnava, so you too should not argue with him."

There is another incident — when Param Gurudeva was enacting his final pastimes while being in poor health.

Hanuman Prasad Prabhu Ji had come from Chandigarh to meet Param Gurudeva.

Guruji and Hanuman Prasad Prabhu together went to the bhajan-kutir (personal room for spiritual practices) of Param Gurudeva, offered their obeisances,  and guruji  requested him to kindly speak some Hari-katha (narrations of the Lord’s glories), especially for  Hanuman Prasad prabhu who had come all the way to hear! Although the doctors had advised Param Gurudeva not to speak much, out of respect for Guruji’s repeated requests, he called all the devotees to his room and one of the many things he spoke was :
"I have no desire to go to the hospital, but by the order of the Vaishnavas, I must go." 

Which vaishnava He was referring to? It was Guruji, as he had repeatedly requested Param Gurudeva to go to the hospital.

Through his life and behavior, Param Gurudeva showed us who a real devotee and pure Vaishnava is.  Even before leaving His body, He declared:
"Bhakti Ballabh Tirtha Goswami Maharaj Ji — must be obeyed by everyone, whether one is a senior or a junior.  Those who accept this may remain here; otherwise, they can leave the Math (monastery)."

The eternal associates of Srila Prabhupada had also previously announced that Guruji had a saintly nature since childhood and would become the future Acharya.

Lord Chaitanya Mahaprabhu has also stated:

"Brahmanda bhramite kona bhāgyavān jīva
Guru-Krishna-prasāde pāya bhakti-latā bīja."

Meaning — Only by the causeless mercy of Supreme Lord and Guru, we can attain the association of a pure Vaishnava or a bona fide spiritual master in our life.

Swami Bhakti Vichar Vishnu Maharaj