Verse 19

आराधयात्मनात्मानमात्मनात्मानमर्चय ।आत्मनात्मानमालोक्य संतिष्ठस्वात्मनात्मनि

In plain words

Worship the ātman by the ātman; adore the ātman by the ātman. Having beheld the ātman by the ātman, abide, by the ātman, in the ātman.