Chandogya Upanishad 5.3

Svetaketu Âruneya went to an assembly of the Pañkâlas. Pravâhana Gaivali said to him: 'Boy, has your father instructed you?' 'Yes, Sir,' he replied.

'Do you know to what place men go from here?' 'No, Sir,' he replied. 'Do you know how they return again?' 'No Sir,' he replied. 'Do you know where the path of Devas and the path of the fathers diverge?' 'No, Sir,' he replied.

"Do you know why that world never becomes full?' 'No, Sir," he replied. 'Do you know why in the fifth libation water is called Man?' 'No, Sir,' he replied.

'Then why did you say (you had been) instructed? How could anybody who did not know these things say that he had been instructed?' Then the boy went back sorrowful to the place of his father, and said: 'Though you had not instructed me, Sir, you said you had instructed me.

'That fellow of a Râganya asked me five questions, and I could not answer one of them.' The father said: 'As you have told me these questions of his, I do not know any one of them. If I knew these questions, how should I not have told you?

Then Gautama went to the kings place, and when he had come to him, the king offered him proper respect. In the morning the king went out on his way to the assembly. The king said to him: 'Sir, Gautama, ask a boon of such things as men possess.' He replied: 'Such things as men possess may remain with you. Tell me the speech which you addressed to the boy.'

The king was perplexed, and commanded him, saying: 'Stay with me some time.' Then he said: 'As (to what) you have said to me, Gautama, this knowledge did not go to any Brâhmana before you, and therefore this teaching belonged in all the worlds to the Kshatra class alone. Then he began: