Madhudviṣa: "Arjuna is recognized by the Lord as a devotee. Therefore one who follows the line of Arjuna in understanding the Gītā will derive benefit from it. Otherwise one will simply waste his valuable time in reading commentaries. Arjuna accepts Śrī Kṛṣṇa as the Supreme Personality of Godhead, and any commentary of the Gītā following in the footsteps of Arjuna is real devotional service to the cause of this great science. But the demons do not accept Lord Kṛṣṇa as He is. The demons concoct something out of their imagination about Kṛṣṇa's instructions. Here is a warning regarding such misleading paths. One should try to follow the disciplic succession from Arjuna and thus be benefited by this great science of the Śrīmad-Bhagavad-gītā."
Prabhupāda: Yes. If we want to study Bhagavad-gītā, then we follow the principles. Just like we have explained this in the introduction, that when you take a bottle of medicine, there is some direction that "Two tablets, twice in a day after meals." So you have to follow the instruction. Then you get benefit. You cannot take any instruction about taking that medicine from a friend or from an expert educationist. No. You have to take direction only from the physician. He is the expert in that line.