John Calvin Commentary Psalms 115:11

"Ye that fear Jehovah, trust in Jehovah: He is their help and their shield." — Psalms 115:11 (ASV)

You who fear Jehovah! He does not speak of strangers, as some erroneously suppose, as if this were a prediction respecting the calling of the Gentiles. Connecting them with the children of Israel and with the sons of Aaron, they believe that he refers to the heathens and to the uncircumcised who were not yet gathered into the sheepfold.

By the same reasoning, one might infer that the priests are not of the seed of Abraham because they are separately mentioned. It is more probable that there is in these words a tacit correction of what he had said before, by which he makes a distinction between the genuine worshippers of God and those hypocrites who were the degenerate sons of Abraham. Many of the seed of Abraham according to the flesh having departed from the faith of their father, the prophet here restricts the promise to those who, having received it by faith, were worshipping God in purity.

We now perceive the reason for his first addressing the Israelites, next the house of Aaron, and then the fearers of Jehovah. It is as if a person in our times were to point his exhortation first to the whole body of the Church, and then come more particularly to the ministers and teachers, who ought to be examples to others.

And as many falsely pride themselves on the mere name of being connected with the Church, and therefore deserve not to be classed with God’s true followers, he expressly mentions the genuine and not the counterfeit worshippers of God.