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

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

They rise upwards who are settled in Harmony; the Active dwell in the mid-most place: the Inert go downwards, enveloped in the vilest

In plain words: Krishna says people rooted in goodness rise upward to higher states. Restless, busy people stay in the middle. Dull, lazy people sink lower, wrapped in the worst qualities.