סימן צח סעיף ז
מֻתָּר לִבְרֹר קִטְנִיּוֹת מַה שֶּׁהוּא צָרִיךְ לְאוֹתוֹ הַיּוֹם, אֲבָל לֹא בְּנַפָּה וְלֹא בִּכְבָרָה, וְגַם לֹא יִתְּנֵם לְתוֹךְ הַמַּיִם כְּדֵי שֶׁיָּצוּף הַפְּסֹלֶת אוֹ הָאֹכֶל, אֶלָּא יִבְרֹר בְיָדוֹ וִילַקֵּט מַה שֶּׁהוּא נֹחַ לוֹ יוֹתֵר. אִם נֹחַ לוֹ לְלַקֵּט הַפְּסֹלֶת, יְלַקֵּט הַפְּסֹלֶת. וְאִם נֹחַ לוֹ לְלַקֵּט הָאֹכֶל יְלַקֵּט הָאֹכֶל (תק"י).
You may sort all the legumes you need for that day,28Unlike Shabbos when, unless it is for immediate use, even separating food from refuse is a melachah de’oraisa. On Yom Tov, separating (boreir) is a melachah de’oraisa only when separating grain (from chaff etc.), which is usually done on a large scale. (Shulchan Aruch Harav 510:3) The Yeshuos Yaakov 500:2 rules that separating two types of foods, even on Yom Tov is permitted only for immediate use. but not with a sieve or strainer.29Since usually a large quantity is separated with these utensils, it looks as though you are doing it for tomorrow’s needs. (Taz 510:1, Mishnah Berurah) Neither may you put them in water so that the refuse or the edible part will float. But you may separate them by hand and pick out whatever is easier for you; if it is easier to pick out the refuse,—pick out the refuse,30Taz and Shulchan Aruch Harav say this is forbidden if you were able to do it before Yom Tov. Biur Halachah 510:2 says since you are not using a sieve etc., it is considered doing it in an unusual manner, and it is permitted even if you could have done it before Yom Tov. But, in such a case it is better to take the food from the refuse; and this is the prevailing custom. and if it is easier to pick out the edible part,—pick out the edible part.
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)