"BLESSED ARE THE MERCIFUL, FOR THEY SHALL RECEIVE MERCY." Historically, this one has been greatly misinterpreted. Readers have concluded that in order to receive mercy, one must first grant mercy. But if that is the case, then we are once again bound by a deadly legalism. If mercy has to be earned by giving it, then it is no longer mercy: it is wages: But mercy is freely given by the one who chooses to do so.
Jesus is actually dealing with those who's mercy causes them to be taken advantage of. They are the ones who are taken advantage of because they are too merciful. The merciful here spoken of are the "pushovers." They are ones who get walked on, who lend money, but fail to have the guts to insist on repayment. Jesus tells these type of folk that when the kingdom invades their life, it will bring the tender mercy of the Heavenly Father.
"BLESSED ARE THE PURE IN HEART, FOR THEY SHALL SEE GOD." This one troubled me for years. How could I ever manage to be so pure as to "see God?" Then I saw it did not mean that I had to do so. As with the other Beatitudes, Jesus is once again speaking to a certain type of people, in this case the perfectionists! The "pure" are perfectionists. To be "pure" is to be singular - to only see things one way. If a substance is pure, it contains only one substance.
Perfectionists cannot function unless everything is in the order they believe it should be in. "Their ducks must all be lined up in a row," as the old saying goes. They cannot eat their toast if it's too dark: nor their cereal if there's too much milk. Perfectionists long for things to be arranged in a certain way, and they have difficulty functioning until they are. But this earth does allow for such a state.
The perfectionists know what is wrong with the world. Actually they are quite miserable people, because earthly affairs are never the way they should be.
The good word that Jesus brings to them is that there is a place in the kingdom for them, also. And, when they enter that kingdom they discover the ONLY ONE THING that is "perfect" - God!
"BLESSED ARE THE PEACEMAKERS, FOR THEY SHALL BE CALLED THE CHILDREN OF GOD." This Beatitude has also been misunderstood. I have seen police officers conclude that they have a special place in heaven because they are in law-enforcement. The soldier sometimes draws this conclusion as well.
But that is not the meaning here. Jesus is saying, however, to the cop and the soldier, or any other "peacemaker," that he, or she, is welcomed into the kingdom, too. And when they step into the kingdom, they are then given a special status: child of God.