Guṇa-Traya-Vibhāga Yoga · Verse 18
ऊर्ध्वं गच्छन्ति सत्त्वस्था मध्ये तिष्ठन्ति राजसाः | जघन्यगुणवृत्तिस्था अधो गच्छन्ति तामसाः
ūrdhvaṃ gacchanti sattva-sthā madhye tiṣṭhanti rājasāḥ | jaghanya-guṇa-vṛtti-sthā adho gacchanti tāmasāḥ
Those abiding in luminosity go upward, the rajasic abide in the middle, those abiding in the lowest quality-activity go downward.
Ūrdhvam — upward — toward higher realms, subtler states of existence, liberation. Madhye — in the middle — the human realm, worldly existence. Adhaḥ — downward — toward lower realms, animal births, hells.
This is not punishment but natural consequence. Like different densities in water, guṇic tendencies determine where consciousness gravitates.
Jaghanya-guṇa-vṛtti — lowest quality-activity — refers to tamas, the guṇa of obscuration and inertia.