וַיִּקַּ֨ח חֶמְאָ֜ה וְחָלָ֗ב וּבֶן־הַבָּקָר֙ אֲשֶׁ֣ר עָשָׂ֔ה וַיִּתֵּ֖ן לִפְנֵיהֶ֑ם וְהֽוּא־עֹמֵ֧ד עֲלֵיהֶ֛ם תַּ֥חַת הָעֵ֖ץ וַיֹּאכֵֽלוּ׃
他拿了奶油、奶，和預備好的小牛，擺在他們面前；他在樹下站在一旁伺候他們，他們就吃了。
Rashi
ויקח חמאה וגו AND HE TOOK חמאה, ETC. — but he did not bring bread, on account of Sarah becoming mentstruant; as the 'way of women' returned to her that day, and the dough became impure (Bava Metzia 87a).
Rashbam
ויקח חמאה וחלב, according to the plain meaning of the text there was no need to report that Avraham supplied the bread which he had volunteered to serve these men. It was only necessary to list the additional items he served, seeing no mention had been made of them thus far.