John Calvin Commentary Psalms 115:2

"Wherefore should the nations say, Where is now their God?" — Psalms 115:2 (ASV)

Why should the heathen say, Where is now their God? They here express how God would maintain His glory in the preservation of the Church. If He permitted the Church to be destroyed, His name would be exposed to the wicked taunts of unbelievers, who would blaspheme the God of Israel as being powerless, because He abandoned His servants in their time of need.

This is not done from the conviction that God requires any such argument, but rather so that the faithful may direct their thoughts back to that holy zeal contained in the words to which we have previously referred: The railings of those that railed against thee have fallen upon me (Psalms 69:10).

And this is the reason for not resorting to rhetorical flourishes to persuade Him to exert His power to preserve the Church; they simply declare that their anxiety for their own safety does not prevent them from valuing the glory of God, as indeed it deserves to be valued more highly.

They go on to show how God’s glory was connected with their deliverance. They declare that He was the Author of the covenant, which the ungodly had boasted was abolished and annulled; and these same individuals had consequently declared that God’s grace was thwarted and His promises were empty.

This is the basis on which they remind Him of His favor and faithfulness, both of which would be subject to malicious slanders if He were to disappoint the hopes of His people. He was bound to them by an everlasting covenant and, in the exercise of His free mercy, had bestowed upon them the privilege of adoption.

And since God, by making us also sharers in His Gospel, has condescended to graft us into the body of His Son, we ought to publicly acknowledge this.