Katha Upanishad Verse 1.3.8
The seeker who possesses discrimination, maintains a controlled and pure mind, reaches the final goal from which there is no rebirth.
Sanskrit Verse
यस्तु विज्ञानवान्भवति समनस्कः सदा शुचिः ।
स तु तत्पदमाप्नोति यस्माद्भूयो न जायते ॥ ८ ॥
Transliteration
yastu vijñānavānbhavati samanaskaḥ sadā śuciḥ |
sa tu tatpadamāpnoti yasmādbhūyo n jāyate || 8 ||
Translation
But he, who knows, who has his mind always under control and who is clean, reaches that goal from which he is not born again.

Muni's Play