यदानन्त्यं प्रतिज्ञाय श्रुतिस्तत्सिद्धये जगौ ।तत्कार्यत्वं प्रपञ्चस्य तद्ब्रह्मेत्यवधारय ॥ ३३ ॥
In plain words
Śruti first declares that it is limitless, and then, to make that limitlessness stand, it sings that this whole spread-out world is nothing but its effect. That is brahman — settle it, and do not waver.
Close to the Sanskrit
Having asserted the infinitude of which, śruti, for the establishing of that, sang the being-an-effect of the manifold universe — ascertain that that is brahman.