In plain words
That is:
asato mā sad gamaya, tamaso mā jyotir gamaya, mṛtyor mā amṛtaṃ gamaya.
The boy who was the first speaker said it: 'vedāham etam puruṣam mahāntam ādityavarṇam tamasaḥ parastāt'. The great ṛṣis searched for God: 'We have recognised God. We have been able to see Him. We have come to know Him.' So they went on proclaiming to all the world. vedāham etam puruṣam mahāntam: we have been able to see that sacred, radiant Puruṣa. We have been able to behold that Puruṣa full of light. Where did we behold Him? In the world outside? No, no. In their own hearts. Where? tamasaḥ parastāt. We have beheld the supreme Puruṣa who is beyond that darkness. Tamas means Ajñāna.
Here we must recognise one thing. Every man grieves at one time or another. If you ask what the cause of this grief is, this very birth is the cause of grief. If there were no birth at all, there would be no grief at all. But what is the cause of this birth? karmānubandhīni manuṣyaloke: it is because of karmas alone that this birth has come to us. What is the cause of this karma? Attachment and hatred themselves are the root cause of karma. If we had no likings at all, we would not do karmas. That is attachment. So attachment and hatred, the two together, have gone on creating karma. What is the basis of this attachment and hatred? It is Ahaṅkāra. 'There is one more handsome than I, there is one who got more marks than I, there is one stronger than I': it is because of Ahaṅkāra of this kind that attachment and hatred begin. What is the root cause of this lack of discrimination? It is Ajñāna. So there is a close tie between this Ajñāna and that grief. That is why grief keeps coming. If Ajñāna is to go, lack of discrimination must be rooted out. If lack of discrimination is to be rooted out, Ahaṅkāra must go. If Ahaṅkāra is to go, attachment and hatred must be subdued. If attachment and hatred are to be subdued, karmas must perish. If karmas are to perish, there must be no life. If there were no life at all, there would be no grief at all. That is why they went on doing sādhanas to make birth fruitful, saying, 'I do not want this birth any more.' Why did they go on longing for birth to come to an end? That is, here is the very reason: 'punar api jananaṃ punar api maraṇam': these two, birth again and death again, have become the cause of grief. If there were no birth and death, we would never be subject to griefs at all. These spiritual sādhanas done to end birth are not merely for some vision, nor to enjoy any other kind of Ānanda beyond experience.