त्वमक्षरं परमं वेदितव्यं त्वमस्य विश्वस्य परं निधानम्। त्वमव्ययः शाश्वतधर्मगोप्ता सनातनस्त्वं पुरुषो मतो मे ॥

tvam akṣharaṁ paramaṁ veditavyaṁ tvam asya viśhvasya paraṁ nidhānam tvam avyayaḥ śhāśhvata-dharma-goptā sanātanas tvaṁ puruṣho mato me

Lofty beyond all thought, unperishing, Thou treasure-house supreme, all-immanent; Eternal Dharma's changeless Guardian, Thou; As immemorial Man I think of Thee.

In plain words: Arjuna praises Krishna as higher than anything the mind can think, never dying, the final resting place of everything, and present in all things. He calls Him the eternal protector of dharma (what is right) and the most ancient Person.