Katha Upanishad Verse 1.3.7

One who lacks discrimination, fails to control their mind, and remains impure does not reach the supreme goal of liberation but continues to cycle through the process of birth and death (Samsara).

Sanskrit Verse

यस्त्वविज्ञानवान्भवत्यमनस्कः सदाऽशुचिः ।
न स तत्पदमाप्नोति सँ सारं चाधिगच्छति ॥ ७ ॥

Transliteration

yastvavijñānavānbhavatyamanaskaḥ sadā’śuciḥ ।
na sa tatpadamāpnoti sam̐ sāraṃ cādhigacchati ॥ 7 ॥

Translation

But he, whose intellect has no discrimination and whose thind is not under control and who is always unclean, does not reach that goal and falls into Samsara.