Bhashya
सः मन्त्रः, यदाह यदुक्तवान् ; कोऽसावर्थ इत्युच्यते— 'असतो मा सद्गमय' इति ।मृत्युर्वा असत्—स्वाभाविककर्मविज्ञाने मृत्युरित्युच्यते ; असत् अत्यन्ताधोभावहेतुत्वात् ; सन् अमृतम्—सत् शास्त्रीयकर्मविज्ञाने, अमरणहेतुत्वादमृतम् ।तस्मादसतः असत्कर्मणोऽज्ञानाच्च, मा माम्, सन् शास्त्रीयकर्मविज्ञाने, गमय, देवभावसाधनात्मभावमापादयेत्यर्थः ।तत्र वाक्यार्थमाह—अमृतं मा कुर्वित्येवैतदाहेति ।तथा तमसो मा ज्योतिर्गमयेति ।मृत्युर्वै तमः, सर्वं ह्यज्ञानमावरणात्मकत्वात्-
In plain words
That mantra—what is its meaning? The text explains: 'From the unreal lead me to the real.' Death is indeed the unreal, spoken of as death in the context of ordinary secular action and knowledge; it is unreal because it leads to extreme downward states. The real is immortality—real in the context of scriptural action and knowledge, and immortal because it prevents death. Therefore, from unreality, from unrighteous action and ignorance, lead me—who am established in scriptural truth—to that real state. The meaning is: 'Cause me to attain the self, which is the means to the divine state.' The import of the sentence is simply: 'Make me immortal.' Similarly, with 'From darkness lead me to light,' death is indeed darkness, for all ignorance has the nature of veiling reality.
Close to the Sanskrit
That mantra, when he spoke, what is that meaning, is stated: 'From the unreal lead me to the real.' Death indeed is the unreal—it is called death in natural action and knowledge; the unreal because of being the cause of extreme downward existence. The real is immortality—the real in scriptural action and knowledge, immortality because of being the cause of non-death. Therefore from the unreal, from unreal action and ignorance, lead me, me, who am real in scriptural action and knowledge, cause [me] to attain the state of the self which is the means to the divine state, is the meaning. There it states the meaning of the sentence: 'It says this very thing: Make me immortal.' Similarly, 'From darkness lead me to light.' Death indeed is darkness, for all ignorance has the nature of veiling.