divi sūrya-sahasrasya
bhaved yugapad utthitā
yadi bhāḥ sadṛśī sā syād
bhāsas tasya mahātmanaḥ
divi — in the sky; sūrya — of suns; sahasrasya — of many thousands; bhavet — there were; yugapat — simultaneously; utthitā — present; yadi — if; bhāḥ — light; sadṛśī — like that; sā — that; syāt — might be; bhāsaḥ — effulgence; tasya — of Him; mahā- ātmanaḥ — the great Lord.
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).