John Calvin Commentary Psalms 150:6

"Let everything that hath breath praise Jehovah. Praise ye Jehovah." — Psalms 150:6 (ASV)

Whatever breathes, etc. Since the word נשמה, neshamah, means breath, or blowing, and refers to whatever is animate or breathes, these words may be extended to every kind of living creature. As we have seen in the preceding psalms, the declaration of God’s praises is assigned even to things lacking intelligence.

However, since humans exclusively are often meant by the term “flesh,” we may very well suppose that the words here refer to humans. Although they share vital breath with the animal creation, they are distinguished by the name “breathing,” as living creatures.

I am led to think this for the following reason: Previously, the Psalmist directed his exhortations to the people who were familiar with the ceremonies under the law. Now, he turns to humanity in general, implicitly indicating that a time was coming when the same songs, then heard only in Judea, would resound throughout the world.

And in this prediction, we have been joined in the same symphony with the Jews, so that we may worship God with constant sacrifices of praise until, being gathered into the kingdom of heaven, we sing with elect angels an eternal hallelujah.