4 Blessed are those who mourn, for they will be comforted.
5 Blessed are the meek, for they will inherit the earth.
6 Blessed are those who hunger and thirst for righteousness, for they will be satisfied.
Why meek does not mean wimpy
I first want to address something skipped in the previous post: the meaning of blessed. R.T. France discusses the difficulty of capturing this Greek word (makarios) in English by choosing happy over the alternatives blessed, congratulations to, and fortunate. After mentioning my favorite alternative, esteemed, he says, Beatitudes are descriptions, and commendations, of the good life.  Jesus commends such a life to his followers.
To say that those who mourn are happy (5:4) is clearly nonsense unless you understand that we are not dealing with a feeling here but rather knowledge that God will comfort them. For what do they mourn? Turner says that, rather than mourning over personal sin or misfortune, they probably mourn over persecution that arises over their allegiance to the kingdom.
The idea that God esteems meekness requires explanation. First, the Greek word praus means, pertaining to not being overly impressed by a sense of ones self-importance, gentle, humble, considerate, meek. Twice Jesus describes himself using this same Greek adjective, and in these instances the NET Bible translates the word as humble (Matt. 11:29) and unassuming (21:5). Further, Moses was described as the meekest man on earth (Num. 12:3). Who would ever say that either Jesus or Moses was not a great leader? Yet both were humble and unassuming. Lovers of swagger, take note!
I like the way Turner puts it: Once again Jesus goes against the grain of human culture and experience by assuming that the meek — not those well stocked with wealth, armament or status — will inherit the earth. You should think long and hard about that statement!
In saying that the meek will inherit the earth (5:5), Jesus points forward to the worldwide kingdom he will rule — assisted by the humble — during the millennium, following his second coming (Rev. 20:4).
One of the best ways to understand the phrase hunger and thirst after righteousness (5:6) is to consider what Jesus said in John 4:34, My food is to do the will of the one who sent me and to complete his work. But what kind of righteousness is he talking about?
Matthew must be understood on his own terms. If you import Pauls meaning for righteousness in Romans into Matthew, you will really be confused. R.T. France says that righteousness in Matthew is overwhelmingly concerned with right conduct, with living the way God requires. A really good example is when Jesus allows John the Baptist to baptize him — over Johns protest (3:14) — in order to fulfill all righteousness (3:15). Jesus had nothing to repent of, but he wanted to identify with those who did. Jesus exemplified the humility mentioned in the previous verse.
Copyright 2011 by Barry Applewhite, Plano, Texas. All rights reserved worldwide. Derived from material created for Christ Fellowship, McKinney, Texas. Used by permission.
 R.T. France, The Gospel of Matthew, The New International Commentary on the New Testament (Grand Rapids: William B. Eerdmans Publishing Company, 2007) 161.
 David L. Turner, Matthew, Baker Exegetical Commentary on the New Testament (Grand Rapids, Baker Academic, 2008) 150, citing Matt. 5:1012, 3848; 10:1642; 13:21; 23:34; 24:9.
 BDAG-3, praus, humble, meek, q.v.
 Turner, Matthew, 151.
 France, Matthew, 167.