B.G 18.15 and 16
śarīravāṅmanobhir yat karma prārabhate naraḥ। nyāyyaṃ vā viparītaṃ vā pañcaite tasya hetavaḥ ॥15॥
Whatever action a man performs with his body, speech, and mind, whether it is just or unjust, these five are its causes.
tatraivaṃ sati kartāraṃ ātmānaṃ kevalaṃ tu yaḥ। paśyatyakṛtabuddhitvānna sa paśyati durmatiḥ ॥16॥
In this situation, the one who perceives the Ātmān, the Lord, as inactive (merely active), due to lack of wisdom, does not truly see, as he is misguided.
Gīta Bhāshya 18.15 and 16
'kartāraṃ ātmānaṃ kevalaṃ' - translates to one who perceives 'Ātmān as merely active, i.e. inactive. One who overlooks the omnipotent aspect of the Lord is foolish.
kevalaṁ niṣkriyam। enaṃ kevalam ātmānaṃ niṣkriyatvād vadanti hi॥ iti tatraiva॥
The word 'kevalam' i.e. limiting, in the context means inactivity. They say - this mere Ātmān is indeed inactive. Hence, the verse 'tatraivaṃ'.