Thanks, Rami, for the clarification regarding "land" and "earth. You've corrected several Christian commentators with regard to that point! Now, on to the fourth Beatitude.
"Blessed are those who hunger and thirst for righteousness, for they will be filled." (Matthew 5:6) (NRSV)
Once again, it's important to note Luke's briefer version: "Blessed are you who are hungry now, for you will be filled." (Luke 6:21) (NRSV) Whatever else Jesus' vision of God's kingdom entailed, it included satisfaction of plain human hunger. I suspect many of those who heard Jesus' words interpreted them in just this fashion. To my way of thinking, this is a sharp reminder that any theology or religious practice that separates the body's needs from spiritual needs is fatally flawed.
During the latter part of the first century, the Christian movement deliberately made provision for feeding the poor and hungry part of its worship and practice. More often than not, an offering of food was taken, that food then being distributed to the hungry. Christian communities became known as places where a hungry person could get a meal. Such communities, at the very least, had caught a bit of the vision of Jesus.
Matthew's account expands the saying's reach to include a hunger and thirst for righteousness. Many of those who heard Jesus would have had experience with hunger. They knew the kind of physical/mental/emotional yearing genuine hunger or thirst generates. Jesus blessed those who had a similar consuming need for rightousness.
What kind of rightousness? I think the most natural and likely answer is the rule of God, the kingdom of God. It's the kind of yearning that causes one to ache for things to be as they are supposed to be, for God's rule to be fully effective in the world at large and in each individual. That which we've thought to be nourishing food and drink now sticks in our throats. If swallowed, it neither feeds or waters us. We know we need something more, something real.
Jesus promised such yearnings would be satisfied. The Greek term "choriasthesoniai" carries the notion of being completely filled. Insofar as I can determine, Jesus believed he had come to begin the fulfillment of the promise.
Let's step away from language, the first century and theology for a moment and ask: "How might the beatitude play out in my life?" That's my primary concern. In my own case, I sometimes find I yearn deeply for God's rule in my life and in the world at large. The simplest way to satisfy (partially) such a hunger is to do something congruent with the active rule of God. Feed a hungry person, intervene in the life of an abused child or spouse, take a loving action toward an enemy--you get the drift.
The world is not the way it ought to be! But each time I act as if God is ruling, I challenge the way of the world. I offer an alternative. Whether the world pays any attention or not, at least for a moment God rules in the small space I occupy, and my hunger is satisfied for a time. Someone else might just experience the loving rule of God through me as well.