Yevamot 37 – Yibum with a pregnant widow

If a woman's husband dies and leaves no son,  the late husband's brother can do a yibum (marriage) or a chalitzah (divorce) with the widow. However, the Sages asked to delay either for three months.

Here is why. Imagine that one marries the late brother's wife only two months after the brother dies. Imagine also that she gives birth seven months after this. Now we have two possibilities. It could be that this child is the full-term baby of the deceased. In this case, yibum was forbidden in the first place, they have transgressed and must bring a sacrifice, and he needs to divorce her because one cannot live with the wife of this brother who died but left a child.

On the other hand, if it is his child born after seven months of pregnancy (in the time of the Talmud, most babies were born after nine months, but a minority of healthy babies were born after seven months.) Now it transpires that he was correct in doing a yibum, and they can continue living together.

However, we cannot distinguish between the two cases: it may be a child of nine months, which means that the marriage is a transgression, or of seven months, in which case the wedding would be a mitzvah. Since they cannot resolve this uncertainty, he still must divorce her, and they bring the sacrifice prescribed for such doubts. But the child is not a mamzer in either case: either it is a child of the late brother or of the live one, and in both cases, it is legitimate.

Art: Mother and Child by Cornelis C. Zwaan