Born into slavery is not being born with a birthright of freedom as found in verse 17. Verse 20 is generally how God describes how he will go out before you to fight your battles. Meditate on the implications of the verses of 1 Samuel 8: 4-19
4 So all the elders of Israel gathered together and came to Samuel at Ramah. 5 They said to him, “You are old, and your sons do not follow your ways; now appoint a king to lead us, such as all the other nations have.”
6 But when they said, “Give us a king to lead us,” this displeased Samuel; so he prayed to the Lord. 7 And the Lord told him: “Listen to all that the people are saying to you; it is not you they have rejected, but they have rejected me as their king. 8 As they have done from the day I brought them up out of Egypt until this day, forsaking me and serving other gods, so they are doing to you. 9 Now listen to them; but warn them solemnly and let them know what the king who will reign over them will claim as his rights.”
10 Samuel told all the words of the Lord to the people who were asking him for a king. 11 He said, “This is what the king who will reign over you will claim as his rights: He will take your sons and make them serve with his chariots and horses, and they will run in front of his chariots. 12 Some he will assign to be commanders of thousands and commanders of fifties, and others to plow his ground and reap his harvest, and still others to make weapons of war and equipment for his chariots. 13 He will take your daughters to be perfumers and cooks and bakers. 14 He will take the best of your fields and vineyards and olive groves and give them to his attendants. 15 He will take a tenth of your grain and of your vintage and give it to his officials and attendants. 16 Your male and female servants and the best of your cattle and donkeys he will take for his own use. 17 He will take a tenth of your flocks, and you yourselves will become his slaves. 18 When that day comes, you will cry out for relief from the king you have chosen, but the Lord will not answer you in that day.”
19 But the people refused to listen to Samuel. “No!” they said. “We want a king over us. 20 Then we will be like all the other nations, with a king to lead us and to go out before us and fight our battles.”
You could ask is Israel redeem through David. There might be an argument in Romans 11 that only a remnant even with David because
Romans 11 The Remnant of Israel
I ask then: Did God reject his people? By no means! I am an Israelite myself, a descendant of Abraham, from the tribe of Benjamin. 2 God did not reject his people, whom he foreknew. Don’t you know what Scripture says in the passage about Elijah—how he appealed to God against Israel: 3 “Lord, they have killed your prophets and torn down your altars; I am the only one left, and they are trying to kill me”? 4 And what was God’s answer to him? “I have reserved for myself seven thousand who have not bowed the knee to Baal.”[b] 5 So too, at the present time there is a remnant chosen by grace. 6 And if by grace, then it cannot be based on works; if it were, grace would no longer be grace.
7 What then? What the people of Israel sought so earnestly they did not obtain. The elect among them did, but the others were hardened, 8 as it is written:
“God gave them a spirit of stupor,
eyes that could not see
and ears that could not hear,
to this very day.”
9 And David says:
“May their table become a snare and a trap,
a stumbling block and a retribution for them.
10 May their eyes be darkened so they cannot see,
and their backs be bent forever.”
Ingrafted Branches
11 Again I ask: Did they stumble so as to fall beyond recovery? Not at all! Rather, because of their transgression, salvation has come to the Gentiles to make Israel envious. 12 But if their transgression means riches for the world, and their loss means riches for the Gentiles, how much greater riches will their full inclusion bring!
13 I am talking to you Gentiles. Inasmuch as I am the apostle to the Gentiles, I take pride in my ministry 14 in the hope that I may somehow arouse my own people to envy and save some of them. 15 For if their rejection brought reconciliation to the world, what will their acceptance be but life from the dead? 16 If the part of the dough offered as firstfruits is holy, then the whole batch is holy; if the root is holy, so are the branches.
17 If some of the branches have been broken off, and you, though a wild olive shoot, have been grafted in among the others and now share in the nourishing sap from the olive root, 18 do not consider yourself to be superior to those other branches. If you do, consider this: You do not support the root, but the root supports you. 19 You will say then, “Branches were broken off so that I could be grafted in.” 20 Granted. But they were broken off because of unbelief, and you stand by faith. Do not be arrogant, but tremble. 21 For if God did not spare the natural branches, he will not spare you either.
22 Consider therefore the kindness and sternness of God: sternness to those who fell, but kindness to you, provided that you continue in his kindness. Otherwise, you also will be cut off. 23 And if they do not persist in unbelief, they will be grafted in, for God is able to graft them in again. 24 After all, if you were cut out of an olive tree that is wild by nature, and contrary to nature were grafted into a cultivated olive tree, how much more readily will these, the natural branches, be grafted into their own olive tree!
All Israel Will Be Saved
25 I do not want you to be ignorant of this mystery, brothers and sisters, so that you may not be conceited: Israel has experienced a hardening in part until the full number of the Gentiles has come in, 26 and in this wayall Israel will be saved. As it is written:
“The deliverer will come from Zion;
he will turn godlessness away from Jacob.
27 And this is my covenant with them
when I take away their sins.”
28 As far as the gospel is concerned, they are enemies for your sake; but as far as election is concerned, they are loved on account of the patriarchs, 29 for God’s gifts and his call are irrevocable. 30 Just as you who were at one time disobedient to God have now received mercy as a result of their disobedience, 31 so they too have now become disobedient in order that they too may now receive mercy as a result of God’s mercy to you. 32 For God has bound everyone over to disobedience so that he may have mercy on them all.
All Israel Will Be Saved? What does that mean exactly.
Roman 9:14-33
14 What then shall we say? Is God unjust? Not at all! 15 For he says to Moses,
“I will have mercy on whom I have mercy,
and I will have compassion on whom I have compassion.”
16 It does not, therefore, depend on human desire or effort, but on God’s mercy. 17 For Scripture says to Pharaoh: “I raised you up for this very purpose, that I might display my power in you and that my name might be proclaimed in all the earth.” 18 Therefore God has mercy on whom he wants to have mercy, and he hardens whom he wants to harden.
19 One of you will say to me: “Then why does God still blame us? For who is able to resist his will?” 20 But who are you, a human being, to talk back to God? “Shall what is formed say to the one who formed it, ‘Why did you make me like this?’” 21 Does not the potter have the right to make out of the same lump of clay some pottery for special purposes and some for common use?
22 What if God, although choosing to show his wrath and make his power known, bore with great patience the objects of his wrath—prepared for destruction? 23 What if he did this to make the riches of his glory known to the objects of his mercy, whom he prepared in advance for glory— 24 even us, whom he also called, not only from the Jews but also from the Gentiles? 25 As he says in Hosea:
“I will call them ‘my people’ who are not my people;
and I will call her ‘my loved one’ who is not my loved one,”
26 and,
“In the very place where it was said to them,
‘You are not my people,’
there they will be called ‘children of the living God.’”[j]
27 Isaiah cries out concerning Israel:
“Though the number of the Israelites be like the sand by the sea,
only the remnant will be saved.
28 For the Lord will carry out
his sentence on earth with speed and finality.”
29 It is just as Isaiah said previously:
“Unless the Lord Almighty
had left us descendants,
we would have become like Sodom,
we would have been like Gomorrah.”
Israel’s Unbelief
30 What then shall we say? That the Gentiles, who did not pursue righteousness, have obtained it, a righteousness that is by faith; 31 but the people of Israel, who pursued the law as the way of righteousness, have not attained their goal. 32 Why not? Because they pursued it not by faith but as if it were by works. They stumbled over the stumbling stone. 33 As it is written:
“See, I lay in Zion a stone that causes people to stumble
and a rock that makes them fall,
and the one who believes in him will never be put to shame.”
Isaiah 10 Seems to again point to what the issue is 'truly relying of the Lord' in verse 20
The Remnant of Israel
Isaiah 10:20-23
20 In that day the remnant of Israel,
the survivors of Jacob,
will no longer rely on him
who struck them down
but will truly rely on the Lord,
the Holy One of Israel.
21 A remnant will return, a remnant of Jacob
will return to the Mighty God.
22 Though your people be like the sand by the sea, Israel,
only a remnant will return.
Destruction has been decreed,
overwhelming and righteous.
23 The Lord, the Lord Almighty, will carry out
the destruction decreed upon the whole land.
Verse 22 "Though your people be like the sand by the sea, Israel,only a remnant will return.Destruction has been decreed, overwhelming and righteous." could be considered a reference to Abraham's blessing in Genesis 22:17
Geneses 22:17 I will surely bless you and make your descendants as numerous as the stars in the sky and as the sand on the seashore. Your descendants will take possession of the cities of their enemies,
Matthew 3 could also be linking into this. John the Baptist is speaking in some ways of the birthright of Abraham as their father..Out of these stones - God will have mercy on who he has mercy. Who warned you to flee from the coming wrath? Could also be a sync to Samuel with God saying warn the people solemnly. When that day comes the Lord will not answer you.
Matthew 3:7-10
7 But when he saw many of the Pharisees and Sadducees coming to where he was baptizing, he said to them: “You brood of vipers! Who warned you to flee from the coming wrath? 8 Produce fruit in keeping with repentance. 9 And do not think you can say to yourselves, ‘We have Abraham as our father.’ I tell you that out of these stones God can raise up children for Abraham. 10 The ax is already at the root of the trees, and every tree that does not produce good fruit will be cut down and thrown into the fire.