There is a big difference in Scripture for man to know that God is the LORD; and for men to know themselves to be but men. However, both are clearly tied together. Before one can know the Living GOD one must realize their feebleness before God. We must realize that we need God. He does not need us.
God is All-Powerful, All-Knowing, and All-Present; He is also Immutable – Unchanging. He is Infinite. Therefore all men ought to fear Him because of who He is.
Hear the words of David,
“Arise, O LORD; let not man prevail: let the heathen be judged in Thy sight. Put them in fear, O LORD: that the nations may know themselves to be but men. Selah.” Psalm 9:19-20 (KJB)
One thing we can rest assured of, is that men and nations will not prevail against God or His people. I will share with you now the commentary of Matthew Henry on these two verses…
“He concludes with prayer that God would humble the pride, break the power, and blast the projects, of all the wicked enemies of his church: “Arise, O Lord! (Psa_9:19), stir up thy self, exert thy power, take thy seat, and deal with all these proud and daring enemies of thy name, and cause, and people.” 1. “Lord, restrain them, and set bounds to their malice: Let not man prevail; consult thy own honour, and let not weak and mortal men prevail against the kingdom and interest of the almighty and immortal God. Shall mortal man be too hard for God, too strong for his Maker?” 2. “Lord, reckon with them: Let the heathen be judges in thy sight, that is, let them be plainly called to an account for all the dishonour done to thee and the mischief done to thy people.” Impenitent sinners will be punished in God’s sight; and, when their day of grace is over, the bowels even of infinite mercy will not relent towards them, Rev_14:10. 3. “Lord, frighten them: Put them in fear, O Lord! (Psa_9:20), strike a terror upon them, make them afraid with thy judgments.” God knows how to make the strongest and stoutest of men to tremble and to flee when none pursues, and thereby he makes them know and own that they are but men; they are but weak men, unable to stand before the holy God – sinful men, the guilt of whose consciences make them subject to alarms. Note, It is a very desirable thing, much for the glory of God and the peace and welfare of the universe, that men should know and consider themselves to be but men, depending creatures, mutable, mortal, and accountable.
In singing this psalm we must give to God the glory of his justice in pleading his people’s cause against his and their enemies, and encourage ourselves to wait for the year of the redeemed and the year of recompences for the controversy of Zion, even the final destruction of all anti-christian powers and factions, to which many of the ancients apply this psalm.” Matthew Henry Commentary