ज्ञानं कर्म च कर्ता च त्रिधैव गुणभेदतः ।
प्रोच्यते गुणसंख्याने यथावच्छृणु तान्यपि ॥ १८.१९ ॥

jñānam karma ca kartā ca tridhaiva guṇa-bhedata: |
procyate guṇa-saṅkhyāne yathāvacchṛṇu tāny-api || 18.19 ||

Krishna now categorizes the six into groups of three and then submits them to a three-fold classification, based on sattva, rajas and tamas, the three guṇas of Nature:

Knowledge, action and the actor become three-fold based on their guṇas, as discussed in the system classifying Guṇas. Listen duly to this also.