Bhagavad Gita Chapter 11, Verse 51
श्रीभगवानुवाच | सुदुर्दर्शं इदं रूपं दृष्टवानसि यन्मम | देवा अप्यस्य रूपस्य नित्यं दर्शनकाङ्क्षिणः ||
śrī-bhagavān uvāca sudurdarśam idaṁ rūpaṁ dṛṣṭavān asi yan mama devā apyasya rūpasya nityaṁ darśana-kāṅkṣiṇaḥ
The Blessed Lord said: This form of Mine that you have seen is very difficult to see. Even the gods are constantly desiring to see this form.
Krishna emphasizes the rarity and difficulty of seeing the cosmic form. 'Sudurdarśam idaṁ rūpaṁ dṛṣṭavān asi yan mama'—this (idam) form (rūpam) of Mine (mama) which (yat) you have seen (dṛṣṭavān asi) is very difficult to see (sudurdarśam). 'Devā apyasya rūpasya nityaṁ darśana-kāṅkṣiṇaḥ'—even (api) the gods (devāḥ) are constantly (nityam) desiring to see (darśana-kāṅkṣiṇaḥ) this form (asya rūpasya). Krishna emphasizes that seeing the cosmic form is extremely rare—even the gods constantly desire to see it but cannot. This verse shows the special nature of the vision granted to Arjuna—it's not something that can be achieved easily, even by the gods. This prepares for Krishna's explanation of the path to see this form through devotion.