p. 246
करोति श्रद्धयोपनिषदा तदेव वीर्यवत्तरं भवति’ इति ।अन्येषाम् अनात्मविदां वैषयिकाणां तावदेव तत् न समृद्धं भवति; यस्य कर्मणो यत्फलं श्रुतं तावन्मात्रफलसाधनं न फलसमृद्धिहेतुर्भवतीत्यर्थः ॥
In plain words
"Whatever one does with faith and with the upaniṣad — that very act becomes far more potent." That is the text. For everyone else — those who do not know the Self, whose attention is entirely on objects — the act does not swell like that. Whatever fruit scripture assigns to a given action, the action delivers exactly that much and no more. It is a means to its stated result; it is not a cause of any increase in it.
Close to the Sanskrit
"...performs with faith, with the upaniṣad — that alone becomes more potent" — thus. For others, for those who do not know the Self, for those given over to sense-objects, that does not become abundant to that extent; the meaning is: for whichever action whatever fruit is declared, it is a means to just that much fruit, and does not become a cause of the increase of fruit.