श्री भगवानुवाच मया प्रसन्नेन तवार्जुनेदं रूपं परं दर्शितमात्मयोगात्। तेजोमयं विश्वमनन्तमाद्यं यन्मे त्वदन्येन न दृष्टपूर्वम् ॥

mayā prasannena tavārjunedaṁ rūpaṁ paraṁ darśhitam ātma-yogāt tejo-mayaṁ viśhvam anantam ādyaṁ yan me tvad anyena na dṛiṣhṭa-pūrvam

Arjuna, by My favour thou hast seen, This loftiest Form by yoga's self revealed! Radiant, all-penetrating, endless, first, That none except thyself hath ever seen.

In plain words: Krishna tells Arjuna that he saw this highest, shining, endless form only because Krishna chose to show it to him as a gift. No one before Arjuna has ever seen it.