We have learned that the mitzva of yibum (levirate marriage) is for a surviving brother to marry his childless brother’s widow so that his brother’s name will be not be “blotted out.” That is to say, the idea is for the yavam to stand in his brother’s stead, and by having children, the family will continue. Thus, if a man dies and he has children, the mitzva of yibum does not come into effect.
What will the halakha be if a man dies having fathered children, but subsequently those children die? Should we say that, in such a case, the mitzva of yibum is revived in order to continue the family?
On this question the halakha is clear – such a situation does not call for a revival of yibum. Interestingly, the source for this that is brought by the Gemara is from (Sefer 3:17): derakheha darkhei no’am ve-khol netivoteha shalom – “her [the Torah’s] ways are the ways of pleasantness, and all of its paths are peaceful.” This is understood to mean that the Torah would not create a situation whereby a woman who is permitted to go and marry will then be called back to have halitza (or even yibum!) with her late husband’s brother, which would create tensions in her new marriage since the implication is that the second marriage is questionable in some way.
The Ritva points out that the suggestion that even a woman with children would be required to undergo halitza when she is widowed since we are concerned that they may die in the future is not a viable option either. After all, in such a case, there is no obligation of yibum at the time that her first husband died, so halitza would have no meaning at that time.
Regarding the source that is brought for this halakha – derakheha darkhei no’am ve-khol netivoteha shalom – we cannot interpret it to mean that the Torah never presents us with a law that is difficult or unpleasant to fulfill. There are many potential situations for a yevama that may very well be unpleasant. Rather the intention of this teaching is (as Tosafot teach on 2a) that the rules of yibum are equal for all, i.e. we do not find that one potential yevama is free to marry anyone and another in the same setting may need to undergo halitza at a later date.