Reference for Sotah 1:2
כֵּיצַד מְקַנֵּא לָהּ. אָמַר לָהּ בִּפְנֵי שְׁנַיִם, אַל תְּדַבְּרִי עִם אִישׁ פְּלוֹנִי, וְדִבְּרָה עִמּוֹ, עֲדַיִן הִיא מֻתֶּרֶת לְבֵיתָהּ וּמֻתֶּרֶת לֶאֱכֹל בַּתְּרוּמָה. נִכְנְסָה עִמּוֹ לְבֵית הַסֵּתֶר וְשָׁהֲתָה עִמּוֹ כְדֵי טֻמְאָה, אֲסוּרָה לְבֵיתָהּ וַאֲסוּרָה לֶאֱכֹל בַּתְּרוּמָה. וְאִם מֵת, חוֹלֶצֶת וְלֹא מִתְיַבָּמֶת:
How does he warn her? If he says to her before two [witnesses]: "Do not speak with a certain man," and she speaks with him, she is still permitted to her house [her husband] and permitted to eat <i>Terumah</i> [if she is married to a priest]. If she meets with him secretly in a house and stays with him long enough to become impure, she is forbidden to her house [her husband] and forbidden to eat <i>Terumah</i>. And if [her husband] dies [childless], she performs the <i>Chalitza</i> ceremony [of release from Levirate marriage] and does not contract a Levirate marriage.