וְעַתָּה֙ כִּ֣י אָמְנָ֔ם כִּ֥י אם גֹאֵ֖ל אָנֹ֑כִי וְגַ֛ם יֵ֥שׁ גֹּאֵ֖ל קָר֥וֹב מִמֶּֽנִּי׃
참으로 나는 네 기업을 무를 자나 무를 자가 나보다 더 가까운 친족이 있으니
English Explanation of Mishnah Yevamot
There are two instances of levirate marriage in the Tanakh, one involving Judah’s sons and daughter-in-law (Genesis 38) and one involving Ruth and Boaz (see Ruth 3:12 and chapter 4). Some of the legal details of these instances do not match those of Deuteronomy. It is sufficient to note that the rabbis follow the laws of Deuteronomy and do not derive the laws of levirate marriage from Genesis or Ruth.