C. F. Keil and Franz Delitzsch on Isaiah 45:15

Isa 45:15

What follows in Isa 45:15 is not a continuation of the words of the Gentiles, but a response of the church to their confession. The nations that have been idolatrous till now, bend in humble spontaneous worship before the church and its God; and at the sight of this, the church, from whose soul the prophet is speaking, bursts out into an exclamation of reverential amazement. “Verily Thou art a mysterious God, Thou God of Israel, Thou Savour.” Literally, a God who hides Himself (mistattēr: the resemblance to μυστηρ-ιώδης is quite an accidental one; the ē is retained in the participle even in pause). The meaning is, a God who guides with marvellous strangeness the history of the nations of the earth, and by secret ways, which human eyes can never discern, conducts all to a glorious issue. The exclamation in Rom 11:33, “O the depth of the riches,” etc., is a similar one.