आधारभूतं यदखण्डमाद्यंशुद्धं परं ब्रह्म सदैकरूपम् ।सन्मात्रमेवास्त्यथ नो विकल्पःसतः परं केवलमेव वस्तु ॥ ६८९ ॥
In plain words
That which forms the indivisible, primordial, pure, and supreme Brahman—eternally unchanging and serving as the underlying substrate—is pure existence alone. There is no room for mental fabrication; beyond existence, there is only the absolute Reality.
Close to the Sanskrit
That which serves as the substrate, indivisible, primordial, pure, supreme Brahman, eternally uniform, is pure existence alone; then there is no mental fabrication, beyond existence is the sole absolute reality.