Bhagavad Gita · 14.18

ऊर्ध्वं गच्छन्ति सत्त्वस्था मध्ये तिष्ठन्ति राजसाः।जघन्यगुणवृत्तस्था अधो गच्छन्ति तामसाः॥

ūrdhvaṁ gachchhanti sattva-sthā madhye tiṣhṭhanti rājasāḥ jaghanya-guṇa-vṛtti-sthā adho gachchhanti tāmasāḥ

Those established in sattva rise upward. Those in rajas remain in the middle. Those abiding in the lowest quality of tamas go downward.

— Bhagavad Gita 14.18

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)