His face darkened
In question: His face became gloomy. His face became sad or serious (gloomy means dark or gloomy).
("When Rabbi Elazar was with Rabbi Shimon, they gathered in the house of the council. The Rabbi's face was filled with tears." - Yerushalmi Shabbat 10, 5)
Translation
Expression (Hebrew)
הִקְדִּירוּ פָּנָיו
Definition (Hebrew)
בְּהַשְׁאָלָה: פָּנָיו נַעֲשׂוּ קוֹדְרִים. פָּנָיו נַעֲשׂוּ עֲצוּבִים אוֹ רְצִינִיִּים (קוֹדֵר מַשְׁמָע אָפֵל אוֹ חָשׁוּךְ).
("כְּשֶׁהָיָה רַבִּי אֶלְעָזָר בִּי רַבִּי שִׁמְעוֹן נִכְנַס לְבֵית הַוַּעַד הָיוּ פָּנָיו שֶׁל רַבִּי מַקְדִּירוֹת"- יְרוּשַׁלְמִי שַׁבָּת י, ה)