How did Saul find out that David had been anointed to be king?

Question

In 1 Samuel 20:31, Saul tells Jonathan that David was a direct, major threat to his reign:

For as long as the son of Jesse lives on the earth, neither you nor your kingdom will be established. Therefore now, send and bring him to me, for he must surely die.

In 1 Samuel 23:17, Jonathan states that both he and Saul were aware that David would become king:

Thus he said to him, “Do not be afraid, because the hand of Saul my father will not find you, and you will be king over Israel and I will be next to you; and Saul my father knows that also.”

In 1 Samuel 24:20, Saul states that he knew that David would become King:

Now, behold, I know that you will surely be king, and that the kingdom of Israel will be established in your hand.

My question is how Saul found out about this. From 1 Samuel 16:1-3 (NASB):

Now the Lord said to Samuel, “How long will you grieve over Saul, since I have rejected him from being king over Israel? Fill your horn with oil and go; I will send you to Jesse the Bethlehemite, for I have selected a king for Myself among his sons.” 2 But Samuel said, “How can I go? When Saul hears of it, he will kill me.” And the Lord said, “Take a heifer with you and say, ‘I have come to sacrifice to the Lord.’ 3 You shall invite Jesse to the sacrifice, and I will show you what you shall do; and you shall anoint for Me the one whom I designate to you.”

This implies that Samuel was at least somewhat secretive about his intention to anoint David King. That being the case, how did Saul and Jonathan find out about this? How widely known was it that David had been anointed King?

Also, the text strongly implies that Saul may well have killed Samuel if he found out (see the linked question as well). Why didn't he ever retaliate against Samuel in any other way if he knew (especially given that he evidently had no qualms about killing priests for petty reasons)? (I can move this last point to a separate question if people think that it should be its own question).

Answer 1

It had already been announced by Samuel that the kingdom was being taken from Saul and given to a better man than he:

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. (1 Sam. 15:28, NKJV)

It is quite possible from the verses following that this was done, if not in public, then before some of the eldership and army leaders.

As the writer develops the story of David's rise, we see David gradually acquiring the oracular accoutrements of the kingship: he receives prophetic guidance from Gad; he inquires of YHWH; he receives Abiathar and the ephod. At the same time, Saul is no longer hearing from God. This was likely a clear indication to the original readers, as well as the participants in the story themselves, that the favor of YHWH was with David now as it had once been with Saul.

So Saul asked counsel of God, “Shall I go down after the Philistines? Will You deliver them into the hand of Israel?” But He did not answer him that day. (1 Sam. 14:37)

Now the prophet Gad said to David, “Do not stay in the stronghold; depart, and go to the land of Judah.” So David departed and went into the forest of Hereth. (1 Sam. 22:5, NKJV)

Therefore David inquired of the LORD, saying, “Shall I go and attack these Philistines?” And the LORD said to David, “Go and attack the Philistines, and save Keilah.” (1 Sam. 23:2, NKJV)

When David knew that Saul plotted evil against him, he said to Abiathar the priest, “Bring the ephod here.” (1 Sam. 23:9, NKJV)

At the same time, we see Saul in various ways in chs. 23 and 24 of 1 Samuel relying on human communication: reports, receiving messengers, receiving larger delegations.

It's also critical to note that Saul's own people knew that YHWH had turned against him and had sent a harassing spirit against him. This comes right after David's anointing and, while Saul didn't immediately know of David's having been anointed, his own court could see that YHWH had turned against Saul's kingship:

13 Then Samuel took the horn of oil and anointed him in the midst of his brothers; and the Spirit of the LORD came upon David from that day forward. So Samuel arose and went to Ramah. 14 But the Spirit of the LORD departed from Saul, and a distressing spirit from the LORD troubled him. 15 And Saul’s servants said to him, “Surely, a distressing spirit from God is troubling you. (1 Sam. 16:13-15)

Answer 2

Another possibility is that Saul knew nothing about the anointing, but foresaw the danger that David might be made king by popular choice, or by the defection of his own followers.

For what the people want from a king is that he should be a strong military leader. The turning point in the relationship seems to have been 1 Samuel ch18 vv6-9. Saul heard the women singing "Saul has slain his thousands, and David his ten thousands" (RSV). Saul was angry and said "What more can he have but the kingdom? And Saul eyed David from that day on". So his "knowledge" that David would become king need be nothing more than a conviction that David's mlitary prestige made his succession almost inevitable, for political reasons alone.

Answer 3

David's anointing may have been well known at the time, perhaps through the the prophets of the time. The text does not cite where this prophecy Abner mentions came from, but it was widely known as a prophecy...

2 Sam 3:17-18 (NASB emphasis added)

¹⁷ Now Abner had consultation with the elders of Israel, saying, “In times past you were seeking for David to be king over you. ¹⁸ Now then, do it! For the Lord has spoken of David, saying, ‘By the hand of My servant David I will save My people Israel from the hand of the Philistines and from the hand of all their enemies.’”

That is why Abner mentioned it and did the honorable thing in attempting to bring the ten northern tribes under David's dominion. So King Saul and Prince Johnathan were quite aware of this also.