यथा प्रदीप्तं ज्वलनं पतङ्गा विशन्ति नाशाय समृद्धवेगाः। तथैव नाशाय विशन्ति लोका स्तवापि वक्त्राणि समृद्धवेगाः ॥

yathā pradīptaṁ jvalanaṁ pataṅgā viśhanti nāśhāya samṛiddha-vegāḥ tathaiva nāśhāya viśhanti lokās tavāpi vaktrāṇi samṛiddha-vegāḥ

As moths with quickened speed will headlong fly Into a flaming light, to fall destroyed, So also these, in haste precipitate, Enter within Thy mouths destroyed to fall.

In plain words: Arjuna compares the warriors to moths flying fast into a flame. Like the moths, they hurry into God's mouths and are destroyed.