US-P18.224ab शास्त्राद् ब्रह्मास्मि नान्योऽहमिति बुद्धिर्भवेद् दृधा ।US-P18.224cd यदायुक्ता तदैवं धीर्यथा देहात्मधीरिति ॥
In plain words
Through scripture, the conviction 'I am Brahman, not separate from it' grows unshakeable. Then the thought that you are an agent no longer holds, any more than the instinctive belief that you are the physical body.
Close to the Sanskrit
When the conviction 'I am Brahman, I am not another' becomes firm from scripture, then the notion of being a doer and the rest is unreasonable, like the conviction that the body is the Self.