The illegitimate Royal candidate
ויהי ממחרת החדש השני ויפקד מקום דוד, ויאמר שאול אל-יהונתן בנו מדוע לא-בא בן-ישי גם-תמול גם-היום אל-הלחם: ויען יהונתן את-שאול נשאל נשאל דוד מעמדי עד-בית לחם: ויאמר שלחני נא כי זבח משפחה לנו בעיר והוא צוה-לי אחי ועתה אם-מצאתי חן בעיניך אמלטה נא ואראה את-אחי על-כן לא-בא אל-שלחן המלך: ויחר-אף שאול ביהונתן ויאמר לו בן-נעות המרדות הלוא ידעתי כי-בחר אתה לבן-ישי לבשתך ולבשת ערות אמך: כי כל-הימים אשר בן-ישי חי על-האדמה לא תכון אתה ומלכותך ועתה שלח וקח אתו אלי כי בן-מות הוא
It was the day after the New Moon, the second day [of Rosh Chodesh], and David’s seat was vacant. Shaul said to his son Yonasan: “Why didn’t the son of Yishai come, neither yesterday nor today to the meal?” Yonasan answered Shaul: “David exceedingly implored me for permission to go to Bethlehem. He said please let me go, as my family’s feast is in the city, and my brother commanded me to be there. Now, if I’ve found favor in your eyes, I’ll slip away and see my family. Therefore, he didn’t come to the King’s banquet”. Shaul became enraged at Yonasan and said to him: “[You are] the son of a rebellious and immoral woman! Behold, I know you have sided with the son of Yishai, to your shame and the shame of your mother’s nakedness! For all of the days that the son of Yishai is on this Earth, your kingdom will never be established. Now, go and send for him to be brought to me, as he is a dead man”
As Shabbos this week coincides with Erev Rosh Chodesh, there is a special Haftarah that is read. It describes the story of David before he became the sole King of Israel, and King Shaul’s growing distrust of him. After Shaul made several attempts to end David’s life, David ran away and went into hiding. He met up with Shaul’s son Yonasan, his most trusted friend. Yonasan couldn’t believe his father would try to do such a thing, and they came up with a plan to confirm Shaul’s intentions. The following two days would be Rosh Chodesh, and as usual the King would have a banquet. As one of the King’s attendants, David was expected to attend. Yonasan was to tell the King that David had to be at his family’s feast. If the King was understanding, then would be proof that he didn’t seek David’s life. If he became infuriated, it would show that David must remain in hiding. What is the significance of this test? Why did David choose this method to determine the King’s intentions? Why would this elicit a furious response from King Shaul?
There’s a Midrash which explains that David had a very sketchy conception. Yishai, David’s father, had been separated from his wife for three years. His wife had a maidservant, and Yishai wanted to have more children. He therefore petitioned her for her cooperation. She wasn’t interested, and asked her master for advice. Yishai’s wife came up with a plan: the maidservant will pretend to be interested, but in the dark she’ll switch with her master. This is what happened, and Yishai’s wife became pregnant with David. Since Yishai didn’t know he had been intimate with his own wife, he and his other sons thought she had committed adultery. David would therefore have the status of a mamzer. David’s status was finally cleared among his family when he was chosen by the prophet Shmuel to become the next King of the Jews.
King Shaul wasn’t pleased that David was a potential rival for his kingship, but initially he wasn’t too concerned. He had no intentions to kill him, as he felt that David’s efforts would prove unsuccessful. Everyone knew David’s sketchy past, and no one would rally behind him. As well, only someone with a prestigious lineage can become King. But that wasn’t his attitude for long.
David’s absence from the royal banquet required a very convincing excuse. Anything short of an apology would be mutinous. David asked Yonasan to give the alibi that David was required to go to his family’s feast back home. Why was this more important than the King’s banquet? Since this was a family get-together, if David was absent, it would confirm the rumors that had spread about David. Everyone would be convinced he was an illegitimate child; he wasn’t a true member of Yishai’s family. Therefore, it was of great importance that David miss the King’s banquet for his family’s feast.
Upon hearing this excuse, King Shaul became enraged. Yonasan’s acceptance of this excuse was evidence he considered David to have a proper lineage. This is why King Shaul said that Yonasan had sided with “the son of Yishai”, meaning Yonasan considered him Yishai’s legitimate son. This would make David a serious candidate for the throne, preventing Yonasan from becoming King. King Shaul couldn’t accept this, and concluded he had to to pursue David to the death.
 Based on Chasam Sofer’s Toras Moshe III, end of Shemini s.v. בהפטרת מחר חדש
 Metzudas Dovid ad. loc.
 Rashi ad. loc.
 This strange phrase is to indicate that King Shaul was concerned people will be surprised that Yonasan loves the one that Shaul hates, implying that they weren’t really father and son. They would conclude that Yonasan’s mother must have committed adultery (Radak ad. loc.)
 I Samuel 20:27-33
 ibid verses 18-42, as per Megillah 31a
 See ibid 19:10-24
 ibid 20:1-7
 Yalkut Me’am Loez to I Samuel 16:11. This story is mentioned in many sources, one of which is Kli Yakar ad. loc. who says he heard it from Rav Shlomo Alkabetz. Rav Alkabetz himself says it’s from a Midrash, the earliest I found being in Yalkut Machiri ad. loc. (c. 14th century), quoting an unnamed Midrash to Psalms 118:19
 The Rama MiPano in his Asara Ma’amaros Ma’amar Chikur HaDin 3:10 explains that Yishai was concerned that since the Torah forbids marrying someone from Moav (Deuteronomy 23:4), his ancestor Boaz should have been forbidden from marrying Ruth (see Ruth 4:13). There had been a debate raging ever since then if the Torah only forbade male members from Moav, or even female. Boaz had ruled the former, and married Ruth. Even though that was the decided ruling (see Yevamos 77a), Yishai, due to his great righteousness, was concerned that perhaps the halacha was not so. He would consequently be forbidden from marrying into the Jewish people. Therefore, he separated physically from his wife.
 Asara Ma’amaros loc. cit.; this was to fulfill ולערב על תנח ידך (see Yevamos 62b). Yalkut Machiri only says that Yishai desired his wife’s maidservant
 Asara Ma’amaros loc. cit. explains that Yishai planned to make a stipulation: If the halacha is that only male members of Moav are forbidden to marry into the Jewish people, then the maidservant should become free and a full member of the Jewish people. He would thus marry her. If, however the halacha is that even female members of Moav are forbidden, then she should remain a maidservant, as he would be allowed to be with her in her present state
 This is the explanation of Yalkut Me’am Loez loc. cit. However, both Asara Ma’amaros and Kli Yakar loc. cit. sound like Yishai eventually knew he had impregnated his wife. They explain that the reason why David was the rejected child (see I Samuel 16:11 and Psalms 118:22) was because he had the status of a ben temurah (see Nedarim 20b), as Yishai was thinking of another woman while he was intimate with his wife. Even though it would be tempting to say that the Yalkut Me’am Loez means like Rashi to Nedarim loc. cit., who explains that benei temurah are almost considered mamzerim, this would be incorrect. He writes explicitly that they thought he was a mamzer since Yishai had been separated from his wife. Cf. Yalkut Machiri, who only mentions that they rejected David because he was completely red. However, the Chasam Sofer himself goes with the explanation that David was considered a ben temurah
 Yalkut Me’am Loez and Chasam Sofer loc. cit.
 I’m not sure how to reconcile this with note 7
 The Chasam Sofer says that everyone would think he wasn’t Yishai’s son, rather he was a child of the maidservant. I’m not sure how this fits with the above sources, as they all say it was Yishai’s wife who gave birth