Mishnah for Oholot 18:4
שְׂדֵה בוֹכִין, לֹא נִטַּעַת, וְלֹא נִזְרַעַת, וַעֲפָרָהּ טָהוֹר, וְעוֹשִׂין מִמֶּנָּה תַנּוּרִים לַקֹּדֶשׁ. וּמוֹדִים בֵּית שַׁמַּאי וּבֵית הִלֵּל שֶׁבּוֹדְקִים לְעוֹשֶׂה פֶסַח, וְאֵין בּוֹדְקִין לִתְרוּמָה. וּלְנָזִיר, בֵּית שַׁמַּאי אוֹמְרִים, בּוֹדְקִין. וּבֵית הִלֵּל אוֹמְרִים, אֵין בּוֹדְקִין. כֵּיצַד הוּא בוֹדֵק. מֵבִיא אֶת הֶעָפָר שֶׁהוּא יָכוֹל לַהֲסִיטוֹ וְנוֹתֵן לְתוֹךְ כְּבָרָה שֶׁנְּקָבֶיהָ דַקִּים, וּמְמַחֶה, אִם נִמְצָא שָׁם עֶצֶם כַּשְּׂעֹרָה, טָמֵא:
A wailing field may not be planted and may not be sown, but its soil is pure and they can make ovens for holy items out of it. And Beit Shammai agree with Beit Hillel that it should be checked for [someone who passed through it and needs to bring] the Paschal offering but it does not need to be checked for [someone who passed through it and wants to eat] <i>Terumah</i> [a portion of a crop given to a Kohen which becomes holy upon separation, and can only be consumed by Kohanim or their household]. For a <i>Nazir</i> [person who has sworn to abstain from all alcohol-related items, haircuts, and impurity], Beit Shammai say they must check but Beit Hillel say they do not need to check. How does one check? He brings soil that can be moved and puts it through a sieve with narrow perforations and crushes it, if he finds a bone the size of a barley grain it is impure.