Tarko 'pratiṣṭhaḥ smṛtayo vibhinnā na cāsāv ṛṣir yasya mataṁ na bhinnam, dharmasya tattvaṁ nihitaṁ guhāyām. Therefore to become pure or to understand the essence of purity is very confidential. It is not to be acquired by our own efforts, by argument or by being expert in scripture or by becoming a philosopher or a similar way. It is very confidential. Then how? Mahājano yena gataḥ sa panthāḥ (Mahābhārata Vana Parva 313.117).
You have to follow a pure devotee, acknowledged devotee.
Similarly, in the Bhagavad-gītā, if we follow Arjuna, then we understand Bhagavad-gītā as it is. But if we don't follow Arjuna, if we follow somebody, Dr. Frog, or create our own interpretation, then we remain impure. So mahājano yena gataḥ sa panthāḥ. We have to follow the footprints of mahājana, great soul. So here is directly you are meeting great soul, Arjuna. He is directly being taught Bhagavad-gītā by the original teacher. Who can be greater authority than Arjuna?
So as Arjuna accepts Bhagavad-gīta, if you accept Bhagavad-gītā in that way, then your study of Bhagavad-gītā is perfect. It is very simple. Therefore I'm saying here that Kṛṣṇa is the original teacher, and Arjuna is the original student. So you follow the original student, you understand Bhagavad-gītā, even Kṛṣṇa is not present before you. He is present by His words. This is the way of following what is pure.