Sanskrit
ज्ञानं कर्म च कर्ता च त्रिधैव गुणभेदतः । प्रोच्यते गुणसङ्ख्याने यथावच्छृणु तान्यपि ॥ १९ ॥
jñānaṃ karma ca kartā ca tridhaiva guṇabhedataḥ procyate guṇasaṅkhyāne yathāvac chṛṇu tāny api
Translation
Knowledge, action and actor in the category of qualities are also said to be severally threefold, from the difference of qualities; hear thou duly these also.
Annie Besant · The Bhagavad-Gita, translated by Annie Besant (4th ed., 1922) — Wikisource · Public Domain
Explanation
Krishna explicitly names the method before applying it: knowledge, action, and the actor are each threefold by guna, and he asks Arjuna to listen carefully as each triad is unpacked in turn. This is the chapter functioning as a capstone — the same three-guna lens chapter 14 used for the whole of nature, and chapter 17 used for faith, food, sacrifice, austerity, and gift, is now run across the entire vocabulary of ethical action.