Bhagavad Gita, Chapter 17, Verse 4

Sâttvika men worship the Devas; Râjasika, the Yakshas and the Râkshasas; the others, the Tâmasika men, the Pretas and the hosts of Bhutas.

What someone actually worships is named here as a real, direct clue to which force dominates them.

Krishna doesn't leave the three modes abstract, he ties each one to a specific, real object of devotion. Worship itself becomes diagnostic, not just descriptive.