jyotiṣām — in all luminous objects; api — also; tat — that; jyotiḥ — the source of light; tamasaḥ — the darkness; param — beyond; ucyate — is said; jñānam — knowledge; jñeyam — to be known; jñāna-gamyam — to be approached by knowledge; hṛdi — in the heart; sarvasya — of everyone; viṣṭhitam — situated.