The Kingdom
Matthew 5:10 Blessed are those who are persecuted on account of righteousness, because theirs is the kingdom of heaven.
Paul, in Hebrews chapter 11, speaking of those who in ancient days went against the “mainstream” and sought obedience to God, explains thus:
“36 And others received trials of mockings and scourgings, then further of bonds and imprisonment. 37 They were stoned, they were cut in pieces - having died by slaughter of the sword, they went about in sheepskins, in goatskins, being in want, being afflicted, being mistreated, 38 (of whom the Society was not worthy,) wandering upon deserts and mountains and in caves and in the holes of the earth. 39 And all, being accredited through the faith, have not acquired the promise 40 of Yahweh, foreseeing for us something better, that not apart from us should they be perfected.”
In other words, they had not acquired it in the flesh, but they will be together with us in the last day.
Preservation
Matthew 5:13 You are the salt of the earth. But if the salt has lost its savor, with what shall it be salted? It avails for nothing more than it is cast outside to be trampled by men!
Salt had a place in the ritual sacrifices, and a “covenant of salt” seems to represent exactly what salt was used for by our ancestors in the ancient world: preservation. “You are the preservation of the earth” would not be out of context. If it were not for the Children of Israel, Yahweh would have long ago destroyed the earth on account of its depravity.
Leviticus 2:13: And every oblation of thy meat offering shalt thou season with salt; neither shalt thou suffer the salt of the covenant of thy God to be lacking from thy meat offering: with all thine offerings thou shalt offer salt.
Numbers 18:19 All the heave offerings of the holy things, which the children of Israel offer unto the LORD, have I given thee, and thy sons and thy daughters with thee, by a statute for ever: it is a covenant of salt for ever before the LORD unto thee and to thy seed with thee.
2 Chronicles 13:5 Ought ye not to know that the LORD God of Israel gave the kingdom over Israel to David for ever, even to him and to his sons by a covenant of salt?
Manifesting the Kingdom
Most of the things which Christ taught in this Sermon on the Mount can also be found in the Old Testament. In reality, He was teaching nothing new, even if He was explaining much of it it differently, for there is nothing new under the sun. Today with Matthew chapters 6 and 7, we shall continue to see that these things which Christ taught His students are timeless, and existed in the Old Testament as well. If our race obeyed His Word, we would have heaven indeed.
Isaiah 49 contains many similar statements to those found in the Sermon on the Mount
Entrance
Matthew 7:21 Not all who say to Me ‘Prince, Prince!’ shall enter into the kingdom of the heavens, but he doing the will of My Father who is in the heavens. 22 Many shall say to Me in that day ‘Prince, Prince, have we not prophesied in Your name, and cast out demons in Your name, and have done many works of power in Your name?’ 23 And then shall I profess to them that ‘Never have I known you! Depart from Me, those who are working at lawlessness!’
No matter what men do or say, the covenants were made only with the children of Israel. Yahweh's words at Amos, where it was spoken to Israel that “you only have I known of all the families of the earth”, have never changed. Even if they seem to do well, the aliens cannot do well, since they can never honestly admit to Yahweh's exclusive relationship with Israel, and with His exclusive promises to preserve Israel. False teachers want to offer preservation to the aliens after the Second Advent, but the Bible makes it clear that only the children of Israel shall inherit the earth.
Matthew 8:11 I say to you that many shall come from east and west and they shall recline with Abraham and Isaak and Jakob in the kingdom of the heavens, 12 but the sons of the kingdom shall be cast out into the outermost darkness. And there shall be weeping and gnashing of teeth!”
The “sons of the kingdom” are those who pretend to have the law and the prophets, those in the seats of authority in Jerusalem, but they are not necessarily Israelites. Actually, many of them are not Israelites, they are usurpers. And that is why they would be put out. This passage should be cross-referenced to Revelation 2:9 and 3:9, which describe those who claim to be Judaeans, but are not, they are of the assembly of the adversary.
Psalm 107:1 O give thanks unto the LORD, for he is good: for his mercy endureth for ever. 2 Let the redeemed of the LORD say so, whom he hath redeemed from the hand of the enemy; 3 And gathered them out of the lands, from the east, and from the west, from the north, and from the south.
Psalm 112: “10 The wicked shall see it, and be grieved; he shall gnash with his teeth, and melt away: the desire of the wicked shall perish.”