Once a guru was teaching his disciples on how the Lord and living entity reside in the heart of every body. The Guru said, “According to the scriptures, two birds (the Lord and living entity) are living in the same tree (body). One bird (the living entity) eats the fruits of the tree which are sweet and sour (happiness and distress). The other bird, (the Lord) simply watches this bird and is not affected by happiness/distress.” Then one of the students raised a question, “How come the Lord situated in our heart is not affected by our happiness/suffering when we are completely influenced by them. We do not see that happening practically anywhere.” The Guru just kept quiet. The student thought that he has cornered the guru and became very proud of his knowledge and started boasting to other students. After a few days the Guru arranged for a grand feast for all the students and he personally served halwa (soaked in ghee) to each one of them after the feast. To this particular student, he served the halwa on his palm and asked him to eat. After eating, he gave washing powder to the student wash his hand as it was stuck with ghee. After this, he gave some more washing powder and asked the student, “Wash your tongue with this.” The student replied, “Why to wash the tongue? The ghee has not stuck at all.” The guru immediately replied, “Does this answer your query? Ghee is just a material substance and it sticks in your hand and not in your tongue. If this is the potency of a material substance, then think of the all powerful Supreme Lord who is beyond the modes. Though He is in everyone’s heart, He is never entangled. If you surrender to Him, you also will become free from all bondage and reach His lotus feet.” The student then understood the answer and asked forgiveness from the Guru.
According to Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura, even though one may have the good fortune to accept a bona fide, highly qualified guru, if one maintains a taste for fruitive activities or mental speculation one’s advancement will be checked. But if a serious student surrenders to a bona fide spiritual master there is absolutely no impediment to the transmission of perfect knowledge and bliss in the devotional service of the Lord – SB Purport 11.3.21
“The dirty wax of egotism accumulated in the heart prevents us from clearly hearing the Lord’s voice within. A guru, with the stick of knowledge, cleans our hearts. Its really ugly to see what may come out, but by following patiently, we keep cleaning.”- Radhanath Swami in The Journey Home book