The reason why it is important to understand that Passover relates to the firstborn instead of all people (at the present time) is because the entire Scripture was written for the chosen overcomers, not for the whole world. Jesus spoke in parables for this reason… to hide the truth from the general masses of humanity, not to explain it to them. Matthew says,

¹⁰ Then the disciples came and said to him, “Why do you speak to them in parables?” ¹¹ And he answered them, “To you it has been given to know the secrets of the kingdom of heaven, but to them it has not been given. ¹² For to the one who has, more will be given, and he will have an abundance, but from the one who has not, even what he has will be taken away. ¹³ This is why I speak to them in parables, because seeing they do not see, and hearing they do not hear, nor do they understand. ¹⁴ Indeed, in their case the prophecy of Isaiah is fulfilled that says:

¹⁶ But blessed are your eyes, for they see, and your ears, for they hear. ¹⁷ For truly, I say to you, many prophets and righteous people longed to see what you see, and did not see it, and to hear what you hear, and did not hear it. (Matthew 13:10-17 ESV)

Later in this same chapter Matthew said,

³⁴ All these things Jesus said to the crowds in parables; indeed, he said nothing to them without a parable. ³⁵ This was to fulfill what was spoken by the prophet:^[e]

The question we face now is, “Why does God make this so hard?” We have to turn back to Isaiah chapter 6, the chapter Jesus quoted above, in order to understand. Following is that chapter in its entirety.

6 In the year that King Uzziah died I saw the Lord sitting upon a throne, high and lifted up; and the train^[a] of his robe filled the temple. ² Above him stood the seraphim. Each had six wings: with two he covered his face, and with two he covered his feet, and with two he flew. ³ And one called to another and said:

⁴ And the foundations of the thresholds shook at the voice of him who called, and the house was filled with smoke. ⁵ And I said: “Woe is me! For I am lost; for I am a man of unclean lips, and I dwell in the midst of a people of unclean lips; for my eyes have seen the King, the Lord of hosts!”

⁶ Then one of the seraphim flew to me, having in his hand a burning coal that he had taken with tongs from the altar. ⁷ And he touched my mouth and said: “Behold, this has touched your lips; your guilt is taken away, and your sin atoned for.”

⁸ And I heard the voice of the Lord saying, “Whom shall I send, and who will go for us?” Then I said, “Here I am! Send me.” ⁹ And he said, “Go, and say to this people:

This chapter begins with God revealing himself to the prophet Isaiah. Immediately upon receiving that revelation Isaiah “mourns” over his sinful condition and realizes he is “poor in spirit,” so poor in fact that he even calls his lips unclean. By responding in this way Isaiah shows that he, initially at least, qualifies to begin walking as an overcomer. In response to his heart’s cry “without guile” God sends a seraphim to touch his lips with a live, hot coal. This represents (is a type of) the baptism of fire (roasting the lamb) that every overcomer must go through. At this point Isaiah qualifies for the ministry of the word of God. God asks who will go to preach for Elohim and Isaiah volunteers. Then God gives him his marching orders. Isaiah will indeed preach the word of God (it is sweet in his mouth), but its outworking will be bitter (eating bitter herbs) because no one will understand him.

Then Isaiah wonders, how long will this go on? How long will it be until people will finally begin to understand your Word? God answers that this will not occur until judgments come and until the holy seed (firstborn, firstfruits, overcomers) are a mere stump in the land, all that is left of that huge tree today which sees itself as the Kingdom of God on earth, the Church. The overcomers will have been the only ones:

1. Who applied the blood of the Passover lamb to the doors and lintel of their lives (souls),
2. Who ate the lamb with unleavened bread (representing a soul without guile and hyprocrisy which has embraced the true doctrine of Christ, or as Paul says, “not with the old leaven, the leaven of malice and evil, but with the unleavened bread of sincerity and truth.”
3. Who ate the lamb with bitter herbs (they submitted to a life of travail and bitterness of soul as they worked out their soul’s salvation in fear and trembling)
4. Who ate the lamb roasted in the fire, not boiled in water or eaten raw (the overcomers submitted to the baptism of fire allowing God’s word to burn the dross, the sin, out of their souls)
5. Who roasted and ate the lamb whole, with its head, legs, and inner parts (they did not pick and choose the words of God they would apply to their lives; to them the Word of God is as a seamless garment which conveys one truth, God’s truth, and one law, and all of it is to be eaten)
6. Who ate the lamb without breaking its bones (Of course the people of Israel did not pick up the whole lamp and pass it around for each person to take a bite of it; they cut the joints and marrow with a sharp knife. This represents the truth of Hebrews 4:12, “For the word of God is living and active, sharper than any two-edged sword, piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart.” Overcomers learn to discern the word of God and submit to the Spirit’s work in them. They understand that the Word seeks to convert their souls, not just bring their spirits a one-time salvation that does not affect their earthly lives)
7. Who ate all the lamb in one night (who consumed Christ’s flesh and blood during their one life time, that is, who assimilated his word into their very souls and made it part of them during their earthly life, thus becoming one flesh with Christ; since they attempted to eat all of Christ what remains of him that was not eaten (not understood or assimilated during their lives) will be “burned in the fire;” it will be imputed to them by faith at their judgment just before their glorification)
8. Who ate the Passover lamb (Christ) with their loins girded (according to Ephesians 6:10-18 they learned of and submitted to Christ having their most vulnerable body parts protected with the belt of truth)
9. Who ate the Lamb with their feet shod with the Gospel of peace (again according to Ephesians 6)
10. Who ate the Lamb with his staff in his hand (the staff or rod represents the blossoming almond tree rod of Jeremiah 1:11; this speaks of new life, resurrected life, which will first be displayed in each overcomer, each firstborn manchild, the firstfruits of God)
11. Who ate the Lamb in haste (in some mystery I don’t understand the obedience of the overcomers hastens the coming of the Day of the LORD according to Peter,
    

    ⁸ But do not overlook this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day. ⁹ The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you,^[a] not wishing that any should perish, but that all should reach repentance. ¹⁰ But the day of the Lord will come like a thief, and then the heavens will pass away with a roar, and the heavenly bodies^[b] will be burned up and dissolved, and the earth and the works that are done on it will be exposed.^[c]

    ¹¹ Since all these things are thus to be dissolved, what sort of people ought you to be in lives of holiness and godliness, ¹² waiting for and hastening the coming of the day of God, because of which the heavens will be set on fire and dissolved, and the heavenly bodies will melt as they burn! ¹³ But according to his promise we are waiting for new heavens and a new earth in which righteousness dwells. (2 Peter 3:8-13)

12. Who became circumcised by faith in Christ before they ate of him, their Lamb (“For in him dwelleth all the fulness of the Godhead bodily. And ye are complete in him, which is the head of all principality and power: In whom also ye are circumcised with the circumcision made without hands, in putting off the body of the sins of the flesh by the circumcision of Christ: Buried with him in baptism, wherein also ye are risen with him through the faith of the operation of God, who hath raised him from the dead. And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses; Blotting out the handwriting of ordinances that was against us, which was contrary to us, and took it out of the way, nailing it to his cross; And having spoiled principalities and powers, he made a shew of them openly, triumphing over them in it. (Colossians 2:9-15)
13. Who came out of Babylon and refused to eat the Passover Lamb with uncircumcised foreigners (overcomers did not fellowship in Christ with those who refused to acknowledge, accept, and consume Christ in faith also)
14. Who ate the Lamb in One House, God’s House, as a firstborn son of God (“Therefore, holy brothers,^[a] you who share in a heavenly calling, consider Jesus, the apostle and high priest of our confession, ² who was faithful to him who appointed him, just as Moses also was faithful in all God’s^[b] house. ³ For Jesus has been counted worthy of more glory than Moses—as much more glory as the builder of a house has more honor than the house itself. ⁴ (For every house is built by someone, but the builder of all things is God.) ⁵ Now Moses was faithful in all God’s house as a servant, to testify to the things that were to be spoken later, ⁶ but Christ is faithful over God’s house as a son. And we are his house if indeed we hold fast our confidence and our boasting in our hope.” (Hebrews 3:1-6, ESV)

Yes, many are called, but few, very few are chosen. For the vast majority of those called the word of God spoken to Isaiah and quoted by Christ has proved true:

“‘Keep on hearing,^[c] but do not understand;
keep on seeing,^[d] but do not perceive.’
¹⁰ Make the heart of this people dull,^[e]
    and their ears heavy,
    and blind their eyes;
lest they see with their eyes,
    and hear with their ears,
and understand with their hearts,
    and turn and be healed.”

I didn’t say it. The LORD said it.

¹⁹ You will say to me then, “Why does he still find fault? For who can resist his will?” ²⁰ But who are you, O man, to answer back to God? Will what is molded say to its molder, “Why have you made me like this?” ²¹ Has the potter no right over the clay, to make out of the same lump one vessel for honorable use and another for dishonorable use? ²² What if God, desiring to show his wrath and to make known his power, has endured with much patience vessels of wrath prepared for destruction, ²³ in order to make known the riches of his glory for vessels of mercy, which he has prepared beforehand for glory— ²⁴ even us whom he has called, not from the Jews only but also from the Gentiles? ²⁵ As indeed he says in Hosea,

²⁷ And Isaiah cries out concerning Israel: “Though the number of the sons of Israel^[c] be as the sand of the sea, only a remnant of them will be saved, ²⁸ for the Lord will carry out his sentence upon the earth fully and without delay.” ²⁹ And as Isaiah predicted,

³⁰ What shall we say, then? That Gentiles who did not pursue righteousness have attained it, that is, a righteousness that is by faith; ³¹ but that Israel who pursued a law that would lead to righteousness^[d] did not succeed in reaching that law. ³² Why? Because they did not pursue it by faith, but as if it were based on works. They have stumbled over the stumbling stone, ³³ as it is written,