Jesus doesn’t make up the Beatitudes on the spot. Each one has several Old Testament referents, and have long been part of the Word of God. What he does do, however, is inject more weight into them from a New Covenant/Kingdom of God context, which means greater glory and greater promises. This follows with the general direction of the history of the people of God (and consequently the history of the world): marching on toward ever greater things.
The most obvious example is the one directed toward the meek, which alludes directly to Psalm 37:11.
Psalm: “But the meek shall inherit the land and delight themselves in abundant peace.”
Matthew: “Blessed are the meek, for they shall inherit the earth.”
But notice the key difference. The “land” has now become the “world.” The potential inheritance has grown.
This is consistant with the rest of the New Testament, as we see hints that the entire earth itself is the new promised land.
Paul says that the promise to Abraham, which in the OT was couched in terms of the “land”, was really that he would be the heir of the world. And we, as his children, have the same inheritance. (Rom. 4:13)
Likewise, Paul tells us in 1 Corinthians 6:2, that the saints are to judge the world. That is, to perform kingly duties, to discern between good and evil while partaking of Jesus, the Tree of Life. That is to be expected, since Revelation 5:10 says explicitly that God has made us both kings and priests, for the purpose of ruling on the earth, which you would think is so obvious and plain written, that no Christian would deny the fact. But we Christians are experts at discounting obvious parts of the Bible, and when we do, we’re called a “scholar.”
Here’s another one. When Paul quotes the fifth commandment in Ephesians 6:2 as still applicable to children, he calls it the first commandment with a promise: “that it may go well with you and that you may live long in the land.” But here, he’s not talking about the old land of Canaan. Why would the Ephesians care about that? Here, as everywhere else in the New Testament, the promise has expanded, and “land” has become “earth.”
It shouldn’t surprise us that God has made some glorious promises for his people. They are so glorious, so gracious, and so world-changing, that its understandable that we find them hard to believe. For some reason, however, we tend to believe that just the opposite is what God has in store for the world.
Which is a just tad ungrateful. It’s like turning down a filet mignon in favor of finding dinner in the dumpster out back, and thinking you’re doing the cook a favor.