What does "Stop trusting in mere humans, who have but a breath in their nostrils. Why hold them in esteem?" mean?

I agree with the other answers, but I thought I would add some historical context for [Isa 2:22]...

 - Isaiah was sharing God's message of pending judgment against Israel in the [Book of Isaiah].  Why was God judging Israel?  Because Israel had a long history of abandoning worship of God in favor of earthly things.  A few examples of many to choose from:

   - [Num 14:2-4] After Caleb and the other eleven spies returned from scouting across the Jordan River, ten of the spies said the people of the land were too powerful.  So, the Israelites lost confidence in God's protection / provision for them and longed to return to Egyptian bondage. (circa 1300 - 1200 B.C.)

   - [1 Sam 8:7] - Israel demanded a King from the prophet, Samuel.  God says this to Samuel: "they have rejected me as their king." (circa 930 B.C)

   - Instead of fully trusting God, Israel's [King Hezekiah] had recently formed an alliance with pagan Egypt [for protection against Assyria] [2 Kings 18:19-21] (circa 701 B.C.)


God's ultimate point behind [Isa 2:22], is that He is asserting Himself as Israel's rightful king (cf [Isa 44:6]), instead of all these human distractions.


[Book of Isaiah]: http://www.biblegateway.com/passage/?search=isa%201:2-4&version=NIV "1:2-4 Hear me, you heavens! Listen, earth! For the Lord has spoken: 'I reared children and brought them up, but they have rebelled against me.  The ox knows its master, the donkey its owner's manger, but Israel does not know, my people do not understand. Woe to the sinful nation, a people whose guilt is great, a brood of evildoers, children given to corruption!  They have forsaken the Lord; they have spurned the Holy One of Israel and turned their backs on him.'"

[Isa 2:22]: http://www.biblegateway.com/passage/?search=isa%202:22&version=NIV "Stop trusting in mere humans, who have but a breath in their nostrils. Why hold them in esteem?"

[1 Sam 8:7]: http://www.biblegateway.com/passage/?search=1%20sam%208:7&version=NIV "And the Lord told him: 'Listen to all that the people are saying to you; it is not you they have rejected, but they have rejected me as their king.'"

[Isa 44:6]: http://www.biblegateway.com/passage/?search=Isa%2044:6&version=NIV "This is what the Lord says - Israel's King and Redeemer, the Lord Almighty: 'I am the first and I am the last; apart from me there is no God.'"

[2 Kings 18:19-21]: http://www.biblegateway.com/passage/?search=2%20kings%2018:19-21&version=NIV "The field commander said to them, 'Tell Hezekiah: This is what the great king, the king of Assyria, says: On what are you basing this confidence of yours? You say you have the counsel and the might for war - but you speak only empty words. On whom are you depending, that you rebel against me?  Look, I know you are depending on Egypt, that splintered reed of a staff, which pierces the hand of anyone who leans on it! Such is Pharaoh king of Egypt to all who depend on him.'"

[Num 14:2-4]: http://www.biblegateway.com/passage/?search=Numbers%2014:2-4&version=NIV "All the Israelites grumbled against Moses and Aaron, and the whole assembly said to them, 'If only we had died in Egypt! Or in this wilderness! Why is the Lord bringing us to this land only to let us fall by the sword? Our wives and children will be taken as plunder. Wouldn't it be better for us to go back to Egypt?'  And they said to each other, 'We should choose a leader and go back to Egypt'"

[for protection against Assyria]: http://en.wikipedia.org/wiki/Hezekiah#Political_moves_and_Assyrian_invasion

[King Hezekiah]: http://en.wikipedia.org/wiki/Hezekiah