וַיָּ֣רֶם הַ֠טַּבָּח אֶת־הַשּׁ֨וֹק וְהֶעָלֶ֜יהָ וַיָּ֣שֶׂם ׀ לִפְנֵ֣י שָׁא֗וּל וַיֹּ֙אמֶר֙ הִנֵּ֤ה הַנִּשְׁאָר֙ שִׂים־לְפָנֶ֣יךָ אֱכֹ֔ל כִּ֧י לַמּוֹעֵ֛ד שָֽׁמוּר־לְךָ֥ לֵאמֹ֖ר הָעָ֣ם ׀ קָרָ֑אתִי וַיֹּ֧אכַל שָׁא֛וּל עִם־שְׁמוּאֵ֖ל בַּיּ֥וֹם הַהֽוּא׃
Da hob der Koch das Schulterstück und was daran war auf und legte es Saul vor. Und [Samuel] sprach: Das ist das Vorbehaltene, leg es dir vor, iss, denn auf diese bestimmte Frist ist es für dich aufbewahrt. Damit wollte [Samuel] bedeuten: Das Volk habe ich [nur zu diesem Zwecke] geladen. Saul aß mit Samuel an jenem Tage.
Shenei Luchot HaBerit
The prophet Samuel alluded to this mystical dimension of Benjamin not having bent his knee to some alien deity when he commanded that the cook bring the portion which he had told him to set aside. Thereupon the cook lifted up the thigh and what was on it, and set it before Saul. Samuel then said: "What has been reserved has been set before you" (Samuel I 9,23-25.) Rav Galanti, in his book Kol Bochim (on Lamentations), elaborates on this when he discusses the verse in Lamentations 4, 18: צדו צעדנו מלכת, "Our steps were checked; we could not walk, etc." I myself have dealt with this verse elsewhere.