פירוש על יבמות 16:1

האשה. לא תנשא – since her husband went [abroad] without children.

Introduction This mishnah deals with a woman whose husband died abroad and she is not sure whether or not she is obligated to have yibbum with his brother.

ולא תתיבם – for perhaps her rival/associate wife gave birth, and if she should say, perform the ritual of removing the shoe of the brother-in-law who refuses to perform levirate marriage, and afterwards marry whomever you want in the world whichever way you turn. They answered in the Gemara (Tractate Yevamot 119b) because a woman whose husband died without children who has performed the rite of Halitzah with a brother of the deceased is disqualified of [marrying into] the priesthood and if she should perform the rite of Halitzah and it is found afterward that her rival/associate wife gave birth to a living child, her Halitzah is not anything, they need to announce concerning her that she is fit for the priesthood, and was not disqualified on account of that rite of ahalitzah. And whomever that it is found at the time of her Halitzah, and is not found at the time where they announced about the Halitzah, it is nothing and she is not disqualified from the priesthood through her and when he sees her afterwards married to a Kohen, he would say that a woman who had performed the rite of Halitzah is permitted to a Kohen.

A woman whose husband and rival wife went to a country beyond the sea, and to whom people came and said, “your husband is dead”, must neither marry nor contract yibbum until she has ascertained whether her rival wife is pregnant. In this case, the husband and a rival wife went abroad, and at that time the husband had no children. Although the wife who remained behind is certain that her husband is dead, she does not know whether she is liable for yibbum, because she doesn’t know if her rival wife had children while abroad. Therefore she cannot remarry.

היתה לה חמות – abroad.

If she had a mother-in-law she need not be concerned [she had another son]. But if [the mother-in-law] departed while pregnant she must be concerned [that another son was born.
Rabbi Joshua says: she need not be concerned. If the husband traveled abroad and at that time he had no brothers, his wife need not be concerned lest her mother-in-law gave birth to a child before her husband died. Perhaps this is because it is uncommon for a woman to give birth to another child after her older child is already married. Furthermore, even if the mother-in-law gave birth, only a male child will make the wife liable for yibbum. This distinguishes this case from the case in section where a child of other sex will exempt the wife from yibbum, and therefore we are concerned lest she be exempt. If, however, the mother-in-law was pregnant when she traveled, the daughter must be concerned, lest she gave birth to a male child. The wife must wait until she is certain that her mother-in-law did not have a boy. Rabbi Judah holds that in this case as well, the wife need not be concerned and may remarry immediately. This is because there are “two doubts”. The mother-in-law may have miscarried (as older women often do), and even if she gave birth to a viable child, the child might be female. In cases of “two doubts”, the halakhah is generally more lenient.

אינה חוששת – perhaps she had been given a levir even though we suspect above lest her rival wife had given birth whether to a male or a female, he exempts her to this one who is performing the duty of levirate marriage but her mother-in-law, if she also gave birth, she would not be needed for her for this one but if she had given birth to male, it is possible to state that perhaps she aborted, and if you can assume that she did not abort, perhaps it was a girl.

יצתה מלאה – pregnant.

חוששת – perhaps she had been given a levir. But the Halakha not according to Rabbi Yehoshua who said that she does not have to worry/scruple [concerning her].