John Calvin Commentary Psalms 64:9

"And all men shall fear; And they shall declare the work of God, And shall wisely consider of his doing." — Psalms 64:9 (ASV)

And all men shall see, and shall declare the work of God. He elaborates on the good effects that would result from the judgment carried out. This judgment would lead those who had previously overlooked Divine Providence entirely to develop a spirit of inquiry due to the uniqueness of the sight. Furthermore, it would lead them to familiarize themselves with, and discuss with one another, a subject previously unknown to them.

He suggests that the knowledge of what God had so remarkably accomplished would spread far and wide — for he says, all men, etc. The Hebrew verb שכל, shachal, employed, admits either of the neuter signification, they shall understand, or of the active, they shall cause others to understand. But as it is usual with David to repeat the same thing twice, perhaps the latter or transitive sense is preferable.

Another desirable consequence that would result from the granted deliverance is mentioned in the last verse. This consequence is that it would provide cause for joy, hope, and holy triumph to the saints. These saints would be strengthened in their expectation of the same help from God that He had extended to His servant David.

Those formerly called the righteous are now called the upright in heart, teaching us that the only righteousness that proves acceptable is that which proceeds from inward sincerity. I have elaborated on this truth extensively elsewhere.