The idea is the Lord said to Arjuna that "This yoga, this system of yoga, Bhagavad-gītā, was first spoken by Me to the sun-god and the sun-god explained to Manu. Manu explained to Ikṣvāku, and in that way, by disciplic succession, one after another, this yoga system is coming, and in course of time this system is now lost. And therefore, I am speaking to you the very same yoga system again, the very same old yoga system of Bhagavad-gītā, or Gītopaniṣad. Because you are My devotee and you are My friend, therefore it is possible for you only to understand."
Now the purport is that Bhagavad-gītā is a treatise which is specially meant for the devotee of the Lord. There are three classes of transcendentalists, namely the jñānī, the yogī and the bhakta. Or the impersonalist or the meditator or the devotees. So here it is clearly mentioned, the Lord says to Arjuna that "I am speaking or I am making you the first man of the paramparā. Because the old paramparā or disciplic succession is now broken, therefore I wish to establish again another paramparā in the same line of thought as it was coming down from the sun-god to others.