|Chapter 11, Verse 12|

दिवि सूर्यसहस्रस्य भवेद्युगपदुत्थिता।

यदि भाः सदृशी सा स्याद्भासस्तस्य महात्मनः।।11.12।।

ॐ

Transliteration / Meaning

divi sūrya-sahasrasya bhaved yugapad utthitā
yadi bhāḥ sadṛiśhī sā syād bhāsas tasya mahātmanaḥ

Translation

If hundreds of thousands of suns were to rise at once into the sky, their radiance might resemble the effulgence of the Supreme Person in that universal form.

Purport by Srila Prabhupada

What Arjuna saw was indescribable, yet Sanjaya is trying to give a mental picture of that great revelation to Dhritarashtra. Neither Sanjaya nor Dhritarashtra was present, but Sanjaya, by the grace of Vyasa, could see whatever happened. Thus he now compares the situation, as far as it can be understood, to an imaginable phenomenon (i.e., thousands of suns).