स य एषोऽणिमैतदात्म्यमिदं सर्वं तत्सत्यं स आत्मा तत्त्वमसि श्वेतकेतो इति भूय एव मा भगवान्विज्ञापयत्विति तथा सोम्येति होवाच ॥ ४ ॥
In plain words
That subtle essence is the soul of all this universe. That is the supreme reality, that is the Self, and you are that, O Śvetaketu. 'Explain this to me further, revered sir.' 'So be it, dear one,' he replied.
Close to the Sanskrit
That which is this subtle essence, this whole world has that as its self. That is the truth, that is the Self, you are that, O Śvetaketu. Explain this to me further, revered sir. So be it, dear one, he spoke.