Midrash su I Samuele 17:55

“Boaz said to his servant who was appointed over the reapers: Whose is this young woman?” (Ruth 2:5).
“Boaz said to his servant who was appointed over the reapers” – over how many was he appointed? Rabbi Eliezer bar Miriam said: He was appointed over forty-two, [as evident] from this [verse]: “Solomon counted all the strangers who were in the land of Israel…[and they were found to be one hundred fifty-three thousand, six hundred]. He set from them seventy thousand porters [and eighty thousand hewers in the mountains, and three thousand six hundred overseers to set the people at work]” (II Chronicles 2:16–17).¹⁶²Having 3,600 overseers for 150,000 workers yields a ratio of one overseer for approximately forty-two workers. One who does so can sustain it and know what each of them is doing.
“Whose is this young woman?” – did he not know who she was? Rather, once he saw that she was pleasant and her actions were fine, he began asking about her. All the women would bend at the waist and gather, and this one would sit and gather. All the women would raise their skirts, and she would lower her skirts. All the women would jest with the reapers, while she would conduct herself modestly. All the women would gather between the sheaves, and she would gather from what had been abandoned.
Similarly, “When Saul saw David emerge against the Philistine [he said to Avner, commander of the army: Avner, whose son is this lad?]” (I Samuel 17:55); did he not know who he was? The day before, he had sent to Yishai saying: “Please let David stand before me, as he has found favor in my eyes” (I Samuel 16:22), and now he is asking about him? Rather, when Saul saw the head of the Philistine in his hand, he began asking about him: If he descends from Peretz, he is a king. If he descends from Zeraḥ, he is a judge.¹⁶³Saul knew that David was from the tribe of Judah but did not know from which of Judah’s sons he descended, from Peretz or Zeraḥ. Apparently, there was a tradition that kings would descend form Peretz. Doeg the Edomite was there at that time, and said to him: Even if he descends from Peretz, is he not disqualified? Is he not of disqualified lineage; does he not descend from Ruth the Moavite? Avner said to him: Has the halakha of: An Amonite and not an Amonite woman, not been introduced? He said to him: If so, an Edomite and not an Edomite woman, an Egyptian and not an Egyptian woman.¹⁶⁴It is forbidden to marry an Edomite or Egyptian convert or his descendants, for three generations since his conversion (Deuteronomy 23:8–9). This is understood to apply to both male and female converts. Why were [Amonite and Moavite converts] barred? Was it not “because they did not meet you with bread and with water; [and they hired against you Bilam son of Beor from Petor, Aram Naharayim, to curse you]” (Deuteronomy 23:5)? The women should have gone out to the women [with bread and water]. Avner temporarily forgot the [reason for this] halakha. Saul said to him: The halakha that you forgot, go and ask Samuel and his court. When he came to Samuel in his court, he said to him: From where did you get this, was it not from Doeg? Doeg is a heretic and will not leave this world in peace. To send you away with nothing¹⁶⁵With no response to Doeg’s argument. is not possible. Rather, it is written: “All the glory of the king’s daughter is inside” (Psalms 45:14); it is not for a woman to go out, it is for a man to go out. “And they hired against you” (Deuteronomy 23:5) – it is for a man to pay wages and not for a woman.
“The servant that was appointed over the reapers answered and said: She is a Moavite young woman who returned with Naomi from the field of Moav” (Ruth 2:6).
“The servant that was appointed over the reapers answered and said: She is a Moavite young woman”; and you said her actions are fine and pleasant? Rather, her mentor cured her.¹⁶⁶Naomi cured her of her Moavite ways. This is derived from the continuation of the verse, “who returned with Naomi from the field of Moav” (Matnot Kehuna). The word returned [shava] can also mean “repented.”

GEMARA: Whence do we learn that (that females are permitted)? R. Jochanan said: From the following passage (I Sam. 17, 55) And when Saul saw David going forth against the Philistine, he said unto Abner, the captain of the army; 'Abner, whose son is this lad?' And Abner said: 'As thy soul liveth, O king, I know it not.' Was it then the fact that he (Saul) did not know him? Behold it is written (Ib. 16, 21) And he (Saul) loved him greatly, and he became his armour-bearer. Shall we assume that his question was regarding David's father? Then our question is: Was he then not known to Saul? Behold it is written (Ib. 17, 12) And the man was old in the days of Saul, belonging to the persons [of high esteem,] whereupon Rab, and according to others R. Abba said: This refers to Jesse, David's father, who came in with the army and went out with the army." [Hence Jesse was well known to Saul.] We must therefore say that Saul thus said unto Abner: "Go and ask whether David is the descendant of Perez or of Zerach. If he is the offspring of Perez, then he is destined to royalty, and a king may break through fences [to cut a way through for his army,] against which no one has the right to protest; but if he is of the progeny of Zerach, then he will merely rise to eminence." But what caused Saul bid Abner to ask of David's origin? Because of his garments, concerning which it is written (Ib., ib., 38) And Saul clothed David with his garments (madav). Why is madav used here? This means that his (Saul's) garments were such as fitted David's stature, although it is written (Ib. 10, 23) And he (Saul) was higher than any of the people from his shoulder and upward. [Saul then said to himself:] "What does this fact that my garments fit him signify? Surely he is destined to become the king." To which Doeg the Adamian remarked: "Before you begin an inquiry as to his fitness to the royalty or not, inquire rather whether he is fit to enter the congregation (to inter-marry with Israelites), because he is of the seed of Ruth the Moabite." Thereupon Abner said to him: "We are taught in a Mishnah: A converted male-Ammouite [is excluded from intermarrying] with Judaeans, but not a female; a converted male-Mo'abite, but not a female." According to your interpretation," remarked Saul, "then in the case of a Mamzer also say that a male is prohibited from entering the congregation but not a female?" "The passage says Mamzer, [which means] anything repulsive, including both sexes." Concerning the Egyptians, let us say also that only male Egyptians are mentioned but not females!" "Here [concerning the Ammonites and Mo'abites] it is different, because the reason [of the restriction] is given in the Torah (Deut. 23, 5) For the reason, that they met you not with bread and with water. The custom is for men to meet with bread and wine, but not for women to meet." Nevertheless the men should have met the Israelites and the women the Israelitish woman [hence the reason is for both]. Thereupon Abner remained silent [and was not able to answer this refutation.] Soon after this (I Sam. 17, 56) And the king said: Ask thou whose son this youth is. Why in the first place call David Na'ar (lad), and then call him elem (youth)? Thus did Saul say to Abner: "This law is concealed from thee, go therefore and inquire in the academy." He finally made inquiry, and they told him: "An Ammonite but not an Ammonitish woman, a Moabite, but not a Moamitish woman." (Fol. 77) Doeg raised all the above objections, which silenced them, [causing them to reverse their decisions,] and they were about to announce that he (David) was not fit to be in the congregation of Israel. Immediately after this [the passage says] (II Sam. 17, 25) And Amassa was the son of a man, whose name was Yithra the Israelite, who had gone into Abigail the daughter of Nachash, etc. And it is written (I Chr. 2, 17) And the father of Amassa was Jether the Ishmaelite, whereupon Raba said: Infer from this that Jether tied a sword around him like an Ishmaelite and said: 'Whoever will not obey this decision shall be stabbed with a sword, for thus have I a tradition from the court of Samuel of Ramathaim: An Ammonite, but not an Ammonitish woman; a Moabite, but not a Moabitish woman.' " But how can such evidence be relied upon? Has not R. Abba said in the name of Rab: "A scholar that renders a decision [concerning a disputed question,] if he rendered the decision prior to the incident he is to be heeded, but not otherwise." Here it is different, because Samuel [the prophet] and his court were then still in existence [and could thus be easily verified.] However, what about the above objection? Here (in Babylon) it was explained because (Ps. 45, 14) All gloriously attired awaited the king's daughter in the inner chamber, [hence the women are exempt from outside duty.] In the Land of Israel, it was inferred, and according to some, R. Isaac said: From the following passage (Gen. 18, 9) And they said unto him where is Sarah thy wife? etc. [Hence the women were exempt from the duty of meeting Israel.]