بِجَلَالِ ذَاتِهِ
In the majesty of His essence.
Jalāl denotes grandeur and exalted majesty, before which created limitation is apparent. Dhāt refers to Allah's actual essence; it is not material substance or an assemblage of parts. Affirming the divine essence differs from claiming to comprehend its modality fully.
The prefixed bāʾ can here express an aspect or association: Allah is praised in consideration of the majesty of His essence. The phrase also emphasizes that no creature shares in that unique divine majesty.
Conclusion: Knowledge of Allah is informed by His established attributes, without implying that finite human imagination can encompass the essence of God.