Reference for Tahorot 7:5
הַמַּנִּיחַ עַם הָאָרֶץ בְּתוֹךְ בֵּיתוֹ לְשָׁמְרוֹ, בִּזְמַן שֶׁהוּא רוֹאֶה אֶת הַנִּכְנָסִין וְאֶת הַיּוֹצְאִין, הָאֳכָלִים וְהַמַּשְׁקִים וּכְלֵי חֶרֶס הַפְּתוּחִים, טְמֵאִים. אֲבָל הַמִּשְׁכָּבוֹת וְהַמּוֹשָׁבוֹת וּכְלֵי חֶרֶס הַמֻּקָּפִין צָמִיד פָּתִיל, טְהוֹרִין. וְאִם אֵינוֹ רוֹאֶה לֹא אֶת הַנִּכְנָסִין וְלֹא אֶת הַיּוֹצְאִין, אֲפִלּוּ מוּבָל, אֲפִלּוּ כָפוּת, הַכֹּל טָמֵא:
One who leaves an <i>am ha'aretz</i> in his house to guard it, as long as he [the homeowner] can see those who are entering and those who are exiting, the food and the drinks and the earthenware vessels that are unsealed are all impure, but the beds and couches and the earthenware vessels closed with a tight seal are all pure. And if he cannot see those entering nor those who are exiting, even if he [the <i>am ha'aretz</i> guard] was being lead [by someone] or was tied up, everything is impure.