Sāṃkhya Kārikā verse 25

sāttvikaḥ ekādaśakaḥ pravartate vaikṛtād ahaṃkārāt |
bhūtādeḥ tanmātraḥ sa tāmasaḥ taijasād ubhayam ||

sattva - clarity; the quality of puritypravarta - engaging in, undertakingahaṃkāra - individuation; conception of individuality; the making of selfbhūta - element; living beingtanmātra - thatness, only that; a rudimentary or subtle element;tamas - obscuring; mental darkness, ignorance, illusion, error; deprived of the eye's light or sight; darkness, gloomubhaya - both