Why didn't Shaul know who David was when David fought Goliath?

Question

In שׁמואל א טז, Shaul is distressed:

14: וְר֧וּחַ יְהוָ֛ה סָ֖רָה מֵעִ֣ם שָׁא֑וּל וּבִֽעֲתַ֥תּוּ רֽוּחַ־רָעָ֖ה מֵאֵ֥ת יְהוָֽה

The spirit of God left him. So his advisers recommend that he get someone to play the harp for him to help. One of his advisers recommends that young David:

18: וַיַּעַן֩ אֶחָ֨ד מֵהַנְּעָרִ֜ים וַיֹּ֗אמֶר הִנֵּ֨ה רָאִ֜יתִי בֵּ֣ן לְיִשַׁי֮ בֵּ֣ית הַלַּחְמִי֒ יֹדֵ֣עַ נַ֠גֵּן וְגִבּ֨וֹר חַ֜יִל וְאִ֧ישׁ מִלְחָמָ֛ה וּנְב֥וֹן דָּבָ֖ר וְאִ֣ישׁ תֹּ֑אַר וַיהוָ֖ה עִמּֽוֹ

David is recommended by name and many really nice qualities are attributed to him: brave, man of war, wise, good looking.

Right away when David comes to Shaul (before he even played any music), Shaul is enamored with David:

21: וַיָּבֹ֤א דָוִד֙ אֶל־שָׁא֔וּל וַֽיַּעֲמֹ֖ד לְפָנָ֑יו וַיֶּאֱהָבֵ֣הֽוּ מְאֹ֔ד וַֽיְהִי־ל֖וֹ נֹשֵׂ֥א כֵלִֽים׃

It says that Shaul loved David very much and made him his attendant. And then he asks David's father Yishai for permission to keep David by his side, because Shaul favored David very much.

22: וַיִּשְׁלַ֣ח שָׁא֔וּל אֶל־יִשַׁ֖י לֵאמֹ֑ר יַעֲמָד־נָ֤א דָוִד֙ לְפָנַ֔י כִּֽי־מָ֥צָא חֵ֖ן בְּעֵינָֽי׃

And David was successful in returning peace to Shaul through his harpistry.

23: וְהָיָ֗ה בִּֽהְי֤וֹת רֽוּחַ־אֱלֹהִים֙ אֶל־שָׁא֔וּל וְלָקַ֥ח דָּוִ֛ד אֶת־הַכִּנּ֖וֹר וְנִגֵּ֣ן בְּיָד֑וֹ וְרָוַ֤ח לְשָׁאוּל֙ וְט֣וֹב ל֔וֹ וְסָ֥רָה מֵעָלָ֖יו ר֥וּחַ הָרָעָֽה

Very nice, right? Seems like Shaul is very close with David, knows who he is, knows who his father is, keeps him close.

Now go to the next chapter (Shmuel Alef 17), the story of Goliath

David is no longer by the side of Shaul, he is back by his father (how did that happen when he was Shaul's close attendant?). And Shaul goes to Emek haElah to fight the Pelishtim, led by Goliath, who challenges and embarasses the Israelite army. We already have been introduced to David twice in the previous chapter (once when Shmuel annointed him, and once when he is brought to Shaul). Yet, now we are introduced to him again, as if we have never met him:

12: וְדָוִד֩ בֶּן־אִ֨ישׁ אֶפְרָתִ֜י הַזֶּ֗ה מִבֵּ֥ית לֶ֙חֶם֙ יְהוּדָ֔ה וּשְׁמ֣וֹ יִשַׁ֔י וְל֖וֹ שְׁמֹנָ֣ה בָנִ֑ים וְהָאִישׁ֙ בִּימֵ֣י שָׁא֔וּל זָקֵ֖ן בָּ֥א בַאֲנָשִֽׁים

David is sent by his father to see how his brothers are doing (the brothers are soldiers int he army, while David, described in the previous chapter as being a brave and strong warrior is not).

Everyone is frightened of Goliath, refusing to answer his challenge. David calls him an ערל (uncircumcised) in verse 26, and when word of this defiance reaches Shaul, David is brought to the king.

There is an implication of some familiarity between David and Shaul in that they do have a conversation seemingly as equals (David never addresses Shaul as if he were a king), but there is also nothing explicit to this point to show that Shaul knew very well who David was.

David kills the Philistine, scares their army into mass retreat, and returns with Goliath's head.

And Shaul asks General Avner (after David speaks with him, when he is going forth to meet Goliath):

55: וְכִרְא֨וֹת שָׁא֜וּל אֶת־דָּוִ֗ד יֹצֵא֙ לִקְרַ֣את הַפְּלִשְׁתִּ֔י אָמַ֗ר אֶל־אַבְנֵר֙ שַׂ֣ר הַצָּבָ֔א בֶּן־מִי־זֶ֥ה הַנַּ֖עַר אַבְנֵ֑ר וַיֹּ֣אמֶר אַבְנֵ֔ר חֵֽי־נַפְשְׁךָ֥ הַמֶּ֖לֶךְ אִם־יָדָֽעְתִּי

56: וַיֹּ֖אמֶר הַמֶּ֑לֶךְ שְׁאַ֣ל אַתָּ֔ה בֶּן־מִי־זֶ֖ה הָעָֽלֶם׃

Whose son is the youth?

Really? Shaul doesn't know whose son is the youth? In the previous chapter he sent word to Yishai (David's father) that he was keeping David close, because Shaul loved David so much. And now he doesn't know who David is?

57: וּכְשׁ֣וּב דָּוִ֗ד מֵֽהַכּוֹת֙ אֶת־הַפְּלִשְׁתִּ֔י וַיִּקַּ֤ח אֹתוֹ֙ אַבְנֵ֔ר וַיְבִאֵ֖הוּ לִפְנֵ֣י שָׁא֑וּל וְרֹ֥אשׁ הַפְּלִשְׁתִּ֖י בְּיָדֽוֹ׃

58: וַיֹּ֤אמֶר אֵלָיו֙ שָׁא֔וּל בֶּן־מִ֥י אַתָּ֖ה הַנָּ֑עַר וַיֹּ֣אמֶר דָּוִ֔ד בֶּֽן־עַבְדְּךָ֥ יִשַׁ֖י בֵּ֥ית הַלַּחְמִֽי׃

And dripping head in hand, only David can supply the answer (none of the king's advisors know who David is, even though they recommended him for his superb qualities one chapter before).

The question

What is going on here?

1. Are the chapters out of order chronologically (and the events of at least the end of chapter 16 happened after those of chapter 17)? This would seem to make the most sense, since otherwise how do you explain how no one knew who David was in chapter 17. If Goliath happened first (establishing David's reputation among Shaul's advisors), then why are they presented in the order given in the text? And is there any source for saying this?
2. If the chapters are chronologically in order, how do we explain the end of chapter 17, when no one knows who David is - not Shaul, not his advisors? Why wouldn't David already be in the army, if he was renowned at this point for being so brave and strong?

(Note: all credit to my brilliant wife for asking the question - I am just the one posting here)

Answer 1

This is a question asked by many commentators, so your wife is in good company :)

I'll bring four of the above-mentioned commentators here:

1. Rashi (Samuel 1, 17, 55) (partial)

   וכי לא היה מכירו והלא כתיב (לעיל טז כא) ויאהבהו מאד ויהי לו נושא כליו אלא ראהו מתנהג בטכסיסי מלכות אמר שאול אם בא ממשפחת פרץ...‏

   Saul indeed knew who David was, but since he saw David act "kingly" (i.e. the way he spoke going out to fight Goliath, etc.), his question to Avner is about David's ancestry, since now Saul is worried about him becoming king. So even though he knew who David was, and who his father was, he was now interested in more details about the family.

2. Metzudat David (there)

   מפני הרוח הרעה שכח שם אביו.‏

   He forgot David's father's name because of the "bad spirit" that lay upon him.

3. Radak (there, partial)

   פירש אדוני אבי ז"ל כי כאשר ראה שאול את דוד יוצא לקראת הפלשתי בלא פחד, שאל לאבנר בן מי זה הנער, כלומר תדע אם ישי אביו היה גבור חיל, שנבטח על גבורת הבן, כי אם הוא גבור בן גבור, יוסיף אומץ. ואבנר לא ידע כי ישי היה זקן בימים ההם...‏

   Radak brings his father's explanation that when Saul saw David's bravery, he asked Avner if his father (Yishai) was also a hero, for if so - this is a man to be reckoned with. Avner didn't know the answer, and later on (see Radak's commentary) David says that indeed he is the son of Yishai - a great man of war.

4. Malbim (there)

   האלהיים יאמרו... כי עת יופיע האור האלהי ויבקע כשחר אורו על איש הרוח, אז יתהפך לאיש אחר, כי קרן אור פניו והוד והדר לפניו, ומצד זה בעת התלבש דוד רוח גבורה וזהר אלהי לא הכירו שאול עתה, וידרוש לאמר מי האיש הרוח הלז. אולם לפי הפשט, אחר ששאול הבטיח לתת את בתו להמנצח את הפלשתי, אז תיכף בהתנדב דוד ללחום אתו עלה על לבו כי בהכרח יצטרך לשלם נדרו ולתת לו את בתו, ולכן דרש תיכף על כבוד בית אביו, לא לדעת שמו, כי ידע ששם אביו ישי, רק לדעת יחוסו ומעלתו, ואמרו בן מי זה הנער אבנר, הוא, אם אביו מיוחס נכבד ונשוא פנים ראוי שיתחתן עם המלך, ואבנר לא ידע מענה על זה כי כבוד ישי לא נודע אז.‏

   He brings first an explanation from the "G-odly ones" (those who explain this based on spiritual rules, the inner holy workings, etc.), that explain that when David expressed such spiritual bravery and faith, this changed him in body and soul, he was filled with spiritual light, so Saul did not recognize him this time. However, the Malbim then says that the simpler explanation is that since Saul promised his daughter to the person who killed Goliath, he is now interested in David's father's (and house's) lineage and honor. So Saul knows who David is, but now wants more information on David's lineage. Later, David answers humbly that they are not of great lineage, but simple servants of the king.

So as you can see, many commentators suggest that indeed Saul knew who David was, but was now asking who's son is he, meaning that he wanted information about David's father and ancestry (whether out of fear for his throne, or to see if he is fit to marry his daughter).

Answer 2

Unlike some of the other commentators mentioned, Ralbag accepts Saul’s question at face value and provides a practical explanation:

רבים יתמהו איך יתכן שלא ידע שאול בן מי הוא וכבר סיפר במה שקדם שכבר שלח שאול מלאכים אל ישי שישב בנו דוד עמו וידמה כי המלך לרוב עסקיו ולרוב הבאים לפניו לא יוכל להכיר כל אחד מהם בפרט ויתבאר מתשובת דוד לו ששאילת שאול לא היתה כי אם לדעת מי הוא כדי שיתבאר לו מאיזו משפחה הוא כי כבר הבטיחהו שיתן לו בתו לאשה

Many have wondered how it is possible that Saul did not know whose son [David] was, when it was already told in what preceded that Saul already sent agents to Jesse that his son David should live with [Saul]. And it seems that the king, on account of his many duties and the many coming before him, was unable to recognize each one individually. And it is clear from David’s answer that Saul’s question was only to ascertain who he was, in order to clarify to [Saul] which family [David] was from, since [Saul] had already promised [David] that he would give him his daughter as a wife.

Answer 3

David was younger than imagined when he killed Goliath; likely 15-years-old. Goliath disdained David because David was a "youth", a boy. You had to be 20-years-old to enter the army. David had 7 older brothers and 2 sisters. Only 3 of David's brothers were in the army. The 4 other, older brothers were younger than 20 (19, 18, 17, & 16) making David 15. David's sisters might have been older or younger. That said, maybe a family had to only contribute so many sons of age to the army, and the others, even of age, were exempted, so the family did not suffer a total loss. David might have been 10-years-old when he first played the harp for Saul. Goliath likely believed the Israelites were mocking him by sending a boy with no armor, no sword, no visible weapons, but a stick. Thus, Goliath did not put on his helmet or did not put his visor down.