מִצְוַת עֲשֵׂה מִן הַתּוֹרָה שֶׁיְּיַבֵּם אָדָם אֵשֶׁת אָחִיו מֵאָבִיו בֵּין מִן הַנִּשּׂוּאִין בֵּין מִן הָאֵרוּסִין אִם מֵת בְּלֹא זֶרַע שֶׁנֶּאֱמַר (דברים כה ה) ״וּבֵן אֵין לוֹ״ (דברים כה ה) ״יְבָמָהּ יָבֹא עָלֶיהָ״. וּמִן הַתּוֹרָה אֵין צָרִיךְ לְקַדֵּשׁ יְבִמְתּוֹ שֶׁזּוֹ אִשְׁתּוֹ הִיא שֶׁהִקְנוּ אוֹתָהּ לוֹ מִן הַשָּׁמַיִם אֶלָּא יָבוֹא עָלֶיהָ. וּכְתֻבָּתָהּ עַל נִכְסֵי בַּעְלָהּ שֶׁמֵּת:
It is a positive commandment of Scriptural law for a man to marry the widow of his paternal brother if he died without leaving children, as [Deuteronomy 25:5] states: "[And one of them dies] childless,... her husband's brother should cohabit with her." [This applies to a widow] from nisu'in, or from erusin. [The childless widow is referred to as a yevamah; the rite through which they marry, yibbum.] Scriptural law does not require a man to consecrate his yevamah, for she is his wife that heaven acquired for him. [All that is necessary] is that he cohabit with her. Her deceased husband's estate is responsible for her marriage contract.
