Yevamos 2:3 - 2:4

לא חולצת ולא מתיבמת – her rival/co-wife and all the more so she herself, and similarly, a barren woman, as it is written (Deuteronomy 25:6): “[The first son] that she bears [shall be accounted to the dead brother that his name not be blotted out in Israel],” excluding a barren woman [ and similarly, the wife of a eunuch born without visible testicles and an androgynous individual does not engage in Halitzah nor levirate marriage, as it states ( there -Deuteronomy 25:5): “[When brothers dwell together and one of them lies] and leaves no son, [the wife of the deceased shall not be married to a stranger, outside the family],” excluding those for whom it is inappropriate for them to have children, and the wife of a convert and the wife of a freed slave does not engage in Halitzah nor levirate marriage, for there is no legal status of consanguinity neither for converts nor slaves, but a barren woman and an elderly women either engages in Halitzah or levirate marriage.

אחותה – [her sister] who is a woman forbidden to a man on account of consanguinity when she is [also] her sister-in-law [widow of her childless brother-in-law] such as, for example, when two sisters fell to him from his two brothers and the one is prohibited upon him because of consanguinity such as when she is his mother-in-law or daughter-in-law, she performs Halitzah or levirate marriage but now did not come in contact with the sister of his levirate relation because someone forbidden on account of consanguinity is not his levirate relation.

שניות – [secondary grade of forbidden relationships seen as incestuous] – forbidden incestuous or adulterous sexual relationships that the Scribes/Soferim decreed upon them which are called prohibitions resulting from a Mitzvah (i.e., based upon the Mitzvah not to deviate from the rulings of the Sages – see Deuteronomy 17:11), for it is a Mitzvah to hearken to the words of the Sages, and which are they? The mother of his mother, and there is no limitation but if it is the father of his mother alone, and the mother of his father, and it has no limitation [and if the father of his father] and the wife of his father’s father, and it has no limitation, and the wife of his mother’s father alone, and the wife of his brother’s father from the mother, and the wife of his mother’s brother, whether from the mother or whether from the father and there is no limitation, and daughter-in-law of his daughter, and the daughter of his son’s daughter and the daughter of the daughter’s daughter and the daughter of’s his son’s son and the daughter of his son’s daughter, and the daughter [of the daughter] of the son of his wife, and the daughter [of the daughter] of his wife’s daughter, and the mother of the mother of his father’s wife, and the mother of [the mother] of his wife’s mother, and the father of the mother of his wife’s mother, and the mother of the father of his father’s wife.

גרושה וחלוצה לכהן הדיוט – such as, for example, that he (i.e., as a Kohen) transgressed his dead brother and had married a divorcee or a woman who had undergone Halitzah, and when he died, she needs Halitzah for Kiddushin/betrothal takes effect in those liable for violating negative commandments, but not levirate marriage, for she is prohibited to him, but to exempt/free her without anything is impossible, for it is not strong to release her, for we derive “her” from the wife’s sister, which is punishable by extirpation.