Reference for Tahorot 7:2

הַמַּנִּיחַ עַם הָאָרֶץ בְּתוֹךְ בֵּיתוֹ עֵר וּמְצָאוֹ עֵר, יָשֵׁן וּמְצָאוֹ יָשֵׁן, עֵר וּמְצָאוֹ יָשֵׁן, הַבַּיִת טָהוֹר, יָשֵׁן וּמְצָאוֹ עֵר, הַבַּיִת טָמֵא, דִּבְרֵי רַבִּי מֵאִיר. וַחֲכָמִים אוֹמְרִים, אֵין טָמֵא אֶלָּא עַד מְקוֹם שֶׁהוּא יָכוֹל לִפְשֹׁט אֶת יָדוֹ וְלִגָּע:

One who leaves an <i>am ha'aretz</i> in his house awake and finds him awake, [or leaves him] asleep and finds him asleep, [or leaves him] awake and finds him asleep, [in these three cases] the house is pure. If [one leaves him] asleep and he finds him awake, the house is impure, according to Rabbi Meir. And the Sages say: things are only impure as far as to where he [the <i>am ha'aretz</i>] could extend his hand and touch.

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