In 1 Samuel 8, Israel demands a king. God feels rejected (1Sa 8:7) but appoints Saul (possibly a late fulfillment of Deuteronomy 17:15). God planned to use Saul and set Saul’s kingdom up forever. But Saul fails. God then revokes His plan of an eternal kingdom for Saul. The Bible describes Saul’s eternal legacy being revoked on two separate occasions:

1Sa 13:13 And Samuel said to Saul, “You have done foolishly. You have not kept the commandment of the LORD your God, which He commanded you. For now the LORD would have established your kingdom over Israel forever.
1Sa 13:14 But now your kingdom shall not continue. The LORD has sought for Himself a man after His own heart, and the LORD has commanded him to be commander over His people, because you have not kept what the LORD commanded you.”

In verse 13, Samuel tells Saul that Saul would have had his kingdom established forever. But Saul sinned. Saul had not waited for Samuel to perform a sacrifice. Saul’s motivation was to rally his troops to fight the Philistines through a morale boosting sacrifice. When Samuel did not show up on time, Saul took matters into his own hands. This angered God, and Samuel informs Saul that his kingdom had now been taken from him. Before this point, God had sought to establish Saul’s kingdom forever. After this point, Saul was lost to God.

Notice the action words. God “would have” established a kingdom. God “sought” a replacement. All of this happened “because” Saul had not obeyed God. The text very clearly shows that God had planned to use Saul and Saul’s lineage to rule over Israel forever. But after God saw that Saul was rebellious, God revoked His plans and decided to form a new plan. This is God reacting to unexpected human behavior. If God had known beforehand that Saul would rebel, God would not have anointed him as king. God also would not have planned to appoint Saul as king forever. God would not have to seek a replacement. God did not expect Saul to act in this manner.

But it seems God gave Saul another chance. In 1 Samuel 15, Saul again disappoints God. This time, Saul did not utterly destroy the enemies that he had conquered. Samuel confronts Saul, tells Saul that Saul’s own kingdom would be taken from him and then Samuel hacks to death the defeated pagan king:

1Sa 15:26 But Samuel said to Saul, “I will not return with you, for you have rejected the word of the LORD, and the LORD has rejected you from being king over Israel.”
1Sa 15:28 So Samuel said to him, “The LORD has torn the kingdom of Israel from you today, and has given it to a neighbor of yours, who is better than you.

It is after this event in which God specifically states that if He knew Saul would rebel in this fashion then God would never had appointed Saul in the first place:

1Sa 15:11 “I greatly regret that I have set up Saul as king, for he has turned back from following Me, and has not performed My commandments.” And it grieved Samuel, and he cried out to the LORD all night.

God is saying, very explicitly, that if He knew Saul would have rebelled then God would not have appointed him. This event seems to have sealed Saul’s fate. After this Saul never seems to be on good footing with God again. It is interesting to note that Saul reigns another 15 more years after this event.

In 1 Samuel 28 (towards the end of Saul’s life), Saul uses a medium to summon Samuel who had died in chapter 25. Samuel, not too happy, reminds Saul that God became Saul’s enemy and had given Saul’s kingdom to David:

1Sa 28:16 Then Samuel said: “So why do you ask me, seeing the LORD has departed from you and has become your enemy?
1Sa 28:17 And the LORD has done for Himself as He spoke by me. For the LORD has torn the kingdom out of your hand and given it to your neighbor, David.
1Sa 28:18 Because you did not obey the voice of the LORD nor execute His fierce wrath upon Amalek, therefore the LORD has done this thing to you this day.

God “tore” the kingdom from Saul (the kingdom God was going to establish forever). God “gave” it to David. Samuel reminds Saul that this was because Saul chose not to obey God. Samuel cites the chapter 15 incident over the chapter 13 incident as the reason. Soon after, Saul dies in battle and David replaces Saul as king.

In 2 Samuel, God reveals to David that the eternal kingdom has now been given to him. This is after David brings the Ark of the Covenant back to Jerusalem and David offers to build God a house. God seems to have been impressed by David’s zeal:

2Sa 7:12 “When your days are fulfilled and you rest with your fathers, I will set up your seed after you, who will come from your body, and I will establish his kingdom.
2Sa 7:13 He shall build a house for My name, and I will establish the throne of his kingdom forever.
2Sa 7:14 I will be his Father, and he shall be My son. If he commits iniquity, I will chasten him with the rod of men and with the blows of the sons of men.
2Sa 7:15 But My mercy shall not depart from him, as I took it from Saul, whom I removed from before you.
2Sa 7:16 And your house and your kingdom shall be established forever before you. Your throne shall be established forever.” ‘ “

In this text, God promises to build Solomon’s kingdom forever (Solomon’s name is not known at this point because he is not born until chapter 12, plus there will be several other competitors for the throne). God promises to punish any wrong doing but God also promises that Solomon would not have his throne be removed in the fashion of Saul. The idea is that even if Solomon turned out like Saul, Solomon’s kingdom would not be taken due to God’s relationship with David.

But David understood that even this unconditional statement could be revoked by God if Solomon becomes wicked. Although God promised not to take away Solomon’s kingdom, David reminds Solomon to follow God:

1Ki 2:1 Now the days of David drew near that he should die, and he charged Solomon his son, saying:
1Ki 2:2 “I go the way of all the earth; be strong, therefore, and prove yourself a man.
1Ki 2:3 And keep the charge of the LORD your God: to walk in His ways, to keep His statutes, His commandments, His judgments, and His testimonies, as it is written in the Law of Moses, that you may prosper in all that you do and wherever you turn;
1Ki 2:4 that the LORD may fulfill His word which He spoke concerning me, saying, ‘If your sons take heed to their way, to walk before Me in truth with all their heart and with all their soul,’ He said, ‘you shall not lack a man on the throne of Israel.’

This is paralleled in 1 Chronicles 28:

1Ch 28:6 Now He said to me, ‘It is your son Solomon who shall build My house and My courts; for I have chosen him to be My son, and I will be his Father.
1Ch 28:7 Moreover I will establish his kingdom forever, if he is steadfast to observe My commandments and My judgments, as it is this day.’
1Ch 28:8 Now therefore, in the sight of all Israel, the assembly of the LORD, and in the hearing of our God, be careful to seek out all the commandments of the LORD your God, that you may possess this good land, and leave it as an inheritance for your children after you forever.
1Ch 28:9 “As for you, my son Solomon, know the God of your father, and serve Him with a loyal heart and with a willing mind; for the LORD searches all hearts and understands all the intent of the thoughts. If you seek Him, He will be found by you; but if you forsake Him, He will cast you off forever.

David understood that God’s promise of an enteral kingdom was conditional on David’s lineage remaining righteous. Although the prophecy was for an “eternal” kingdom and God had promised to show mercy after correction, God still could revoke His promise based on the actions of any king. If Solomon or Solomon’s heir were to forsake God, then their eternal kingdom would no longer be enteral.

Solomon acknowledges this conditional prophecy:

1Ki 8:25 Therefore, LORD God of Israel, now keep what You promised Your servant David my father, saying, ‘You shall not fail to have a man sit before Me on the throne of Israel, only if your sons take heed to their way, that they walk before Me as you have walked before Me.’
1Ki 8:26 And now I pray, O God of Israel, let Your word come true, which You have spoken to Your servant David my father.

Paralleled in 1 Chronicles 6:

2Ch 6:15 You have kept what You promised Your servant David my father; You have both spoken with Your mouth and fulfilled it with Your hand, as it is this day.
2Ch 6:16 Therefore, LORD God of Israel, now keep what You promised Your servant David my father, saying, ‘You shall not fail to have a man sit before Me on the throne of Israel, only if your sons take heed to their way, that they walk in My law as you have walked before Me.’
2Ch 6:17 And now, O LORD God of Israel, let Your word come true, which You have spoken to Your servant David.

Solomon points out that only if Solomon and his sons listen to God will God continue Solomon’s lineage. Chronicles points out that they must follow God’s law. This entire section represents Solomon praising God for faithfulness and also petitioning God to fulfill God’s promises in the future. The conditional nature of the eternal kingdom is highlighted.

When God speaks back to Solomon, the conditional nature of the eternal kingdom is again highlighted. God cites His original promise and warns Solomon that the eternal kingdom could be taken for disobedience:

1Ki 9:4 Now if you walk before Me as your father David walked, in integrity of heart and in uprightness, to do according to all that I have commanded you, and if you keep My statutes and My judgments,
1Ki 9:5 then I will establish the throne of your kingdom over Israel forever, as I promised David your father, saying, ‘You shall not fail to have a man on the throne of Israel.’
1Ki 9:6 But if you or your sons at all turn from following Me, and do not keep My commandments and My statutes which I have set before you, but go and serve other gods and worship them,
1Ki 9:7 then I will cut off Israel from the land which I have given them; and this house which I have consecrated for My name I will cast out of My sight. Israel will be a proverb and a byword among all peoples.
1Ki 9:8 And as for this house, which is exalted, everyone who passes by it will be astonished and will hiss, and say, ‘Why has the LORD done thus to this land and to this house?’
1Ki 9:9 Then they will answer, ‘Because they forsook the LORD their God, who brought their fathers out of the land of Egypt, and have embraced other gods, and worshiped them and served them; therefore the LORD has brought all this calamity on them.’ “

Paralleled in 2 Chronicles 7:

2Ch 7:17 As for you, if you walk before Me as your father David walked, and do according to all that I have commanded you, and if you keep My statutes and My judgments,
2Ch 7:18 then I will establish the throne of your kingdom, as I covenanted with David your father, saying, ‘You shall not fail to have a man as ruler in Israel.’
2Ch 7:19 “But if you turn away and forsake My statutes and My commandments which I have set before you, and go and serve other gods, and worship them,
2Ch 7:20 then I will uproot them from My land which I have given them; and this house which I have sanctified for My name I will cast out of My sight, and will make it a proverb and a byword among all peoples.
2Ch 7:21 “And as for this house, which is exalted, everyone who passes by it will be astonished and say, ‘Why has the LORD done thus to this land and this house?’
2Ch 7:22 Then they will answer, ‘Because they forsook the LORD God of their fathers, who brought them out of the land of Egypt, and embraced other gods, and worshiped them and served them; therefore He has brought all this calamity on them.’ “

God’s warning is very harsh. God’s promised eternal kingdom is conditional on the kings who rule over it. If the kings worship other gods, God will revoke His promise and destroy the eternal kingdom. But as long as the kings are faithful to God, God will be faithful to the kings.

Solomon ends up rebelling against God in his old age. God, furious, decides to revoke the promise of an eternal kingdom:

1Ki 11:11 Therefore the LORD said to Solomon, “Because you have done this, and have not kept My covenant and My statutes, which I have commanded you, I will surely tear the kingdom away from you and give it to your servant.
1Ki 11:12 Nevertheless I will not do it in your days, for the sake of your father David; I will tear it out of the hand of your son.
1Ki 11:13 However I will not tear away the whole kingdom; I will give one tribe to your son for the sake of my servant David, and for the sake of Jerusalem which I have chosen.”

Notice God’s intense change of plans. God dissolved His promise of an eternal kingdom, but for David’s sake allowed a fractional kingdom to continue.

In conclusion:

God sought to give Saul an eternal kingdom but revoked that plan after Saul rebelled. God then regretted ever making Saul king and wished that He had not.

God then gave David the eternal kingdom, but this too was conditional (although originally not explicit, David, Solomon, and God later emphasized the conditional nature of this eternal kingdom). God did not seem to know when or if David’s lineage would ever forsake God. The eternal kingdom was only eternal if certain conditions were met.

Solomon inherited this promise, but things did not end well. Solomon started loyal to God but forsook God later in life. God then dissolved His promise and split the eternal kingdom into two parts, allowing David’s lineage to continue reigned over a fractional piece of the original promised kingdom.

God’s promises, although they look unconditional and promise something eternal, can be revoked if the actions of man warrant revocation. God can change plans at will and respond to unpredicted behaviors of human beings. As stated in Jeremiah 18, if a nation rebels against God, God is not bound to the promises He made to them.