न तु मां शक्यसे द्रष्टुमनेनैव स्वचक्षुषा। दिव्यं ददामि ते चक्षुः पश्य मे योगमैश्वरम् ॥

na tu māṁ śhakyase draṣhṭum anenaiva sva-chakṣhuṣhā divyaṁ dadāmi te chakṣhuḥ paśhya me yogam aiśhwaram

But verily thou art not able to behold Me with these thine eyes; the divine eye I give unto thee. Behold My sovereign Yoga.

In plain words: Krishna explains that Arjuna cannot see this form with his normal eyes. So Krishna gives him a "divine eye," a special power of sight, so he can see Krishna's full power.