John Calvin Commentary Psalms 118:15

"The voice of rejoicing and salvation is in the tents of the righteous: The right hand of Jehovah doeth valiantly." — Psalms 118:15 (ASV)

The voice of shouting and salvation is in the tabernacles of the just. He affirms that the kindness God had bestowed on him was so extensive that thanking him privately would not suffice. In the benefits he had received, God’s power appeared both remarkable and memorable, and its fruit also extended to the whole Church.

Therefore, as David’s deliverance was wonderful and advantageous to all the godly, he promises that he would offer public thanksgiving and invites them to join him in this holy exercise. By this, he chiefly aims to magnify God’s grace. He also seeks to demonstrate by its effects that not only his individual preservation but also that of the whole Church, in his person, was accomplished.

Communion among believers indeed binds them reciprocally to thank God for each other. In David’s case, there was the specific reason I have mentioned: his wonderful preservation from many deaths, and God having assigned him the sovereignty over God’s chosen people. It is noteworthy that he combines the voice of joy and gladness with the praise of God, thereby showing that believers should mingle a sense of God’s grace with their mirth.

The phrase To do valiantly, is equivalent to a magnificent display of his power, resulting in a bright manifestation of its radiance. God often secretly, and when his power seems hidden, grants deliverance to his faithful people, so that they may perceive that it comes from him; but this is not so well known to others.

Here, however, David asserts that God’s work was so clearly revealed that no one could doubt from where his safety came. The other phrase, that the right hand of God was exalted, refers to the same subject, because by working powerfully and extraordinarily, God had exalted his hand.