Christians today are also God's people in His New Covenant. Note that this is separate from salvation
Christ the promised Messiah is the fulfillment of the Old Covenant. Those who reject Jesus reject their own covenant.
Mat 3: 9 do not presume to say to yourselves, “We have Abraham as our father’; for I tell you, God is able from these stones to raise up children to Abraham. Even now the axe is laid to the root of the trees; every tree therefore that does not bear good fruit is cut down and thrown into the fire.
Luke 13: 6 And he told this parable: “A man had a fig tree planted in his vineyard; and he came seeking fruit on it and found none. And he said to the vinedresser, “Lo, these three years I have come seeking fruit on this fig tree, and I find none. Cut it down; why should it use up the ground?’ And he answered him, “Let it alone, sir, this year also, till I dig about it and put on manure. And if it bears fruit next year, well and good; but if not, you can cut it down.’ “
Luke 14: 16 “A man once gave a great banquet, and invited many; and at the time for the banquet he sent his servant to say to those who had been invited, “Come; for all is now ready.’ But they all alike began to make excuses. The first said to him, “I have bought a field, and I must go out and see it; I pray you, have me excused.’ And another said, “I have bought five yoke of oxen, and I go to examine them; I pray you, have me excused.’ And another said, “I have married a wife, and therefore I cannot come.’ So the servant came and reported this to his master. Then the householder in anger said to his servant, “Go out quickly to the streets and lanes of the city, and bring in the poor and maimed and blind and lame.’
Luke 16: 31 He said to him, “If they do not hear Moses and the prophets, neither will they be convinced if some one should rise from the dead.’ “
Luke 20: 13 Then the owner of the vineyard said, “What shall I do? I will send my beloved son; it may be they will respect him.’ But when the tenants saw him, they said to themselves, “This is the heir; let us kill him, that the inheritance may be ours.’ And they cast him out of the vineyard and killed him. What then will the owner of the vineyard do to them? He will come and destroy those tenants, and give the vineyard to others.” When they heard this, they said, “God forbid!”
John 1: 11 He came to his own home, and his own people received him not. But to all who received him, who believed in his name, he gave power to become children of God; who were born, not of blood nor of the will of the flesh nor of the will of man, but of God.
John 4: 35 Do you not say, “There are yet four months, then comes the harvest’? I tell you, lift up your eyes, and see how the fields are already white for harvest. He who reaps receives wages, and gathers fruit for eternal life, so that sower and reaper may rejoice together. For here the saying holds true, “One sows and another reaps.’ I sent you to reap that for which you did not labor; others have labored, and you have entered into their labor.”
John 5: 39 You search the scriptures, because you think that in them you have eternal life; and it is they that bear witness to me; yet you refuse to come to me that you may have life. I do not receive glory from men. But I know that you have not the love of God within you. I have come in my Father’s name, and you do not receive me; if another comes in his own name, him you will receive. How can you believe, who receive glory from one another and do not seek the glory that comes from the only God? Do not think that I shall accuse you to the Father; it is Moses who accuses you, on whom you set your hope.