When a man will have two wives, one who is beloved and one who is disliked, and the beloved and disliked wife give birth to children for him; and the son of the disliked wife is the first-born… (Devarim 21:15)
1. The rights of the firstborn son cannot be transferred to a preferred son This pasuk introduces laws concerning inheritance. The Torah explains that a father’s firstborn son inherits a double portion of the property of the father. This law applies even in the special case in our pasuk. In this instance, the father has two wives. One is beloved. The other is shunned. The father’s firstborn is the child of the shunned wife. The father cannot disregard the inheritance rights of this son. He receives a double portion. In other words, the father cannot transfer this right to a younger son from the beloved wife.
2. The unique mitzvah of Yefat Torah and its rationale Rashi explains that this law is related to the previous discussion in the parasha. In that section the law of Yefat Toar is presented. The Yefat Toar is a non-Jewish woman captured in battle. The Torah allows the soldier to have a sexual encounter with this non-Jewish woman. However, if the man wishes to marry the woman and enter into a more permanent relationship, then she must accept Judaism.
Why does the Torah allow the soldier to have relations with this non-Jewish woman? Our Sages explain that the Torah recognizes the force of the desires awakened in the violence of war. The Torah assumes that these powerful instincts will overpower many soldiers. These warriors will not be able to resist the desire to enter into sexual relations with the captive women. This creates a dilemma. Enforcement of the normal prohibition against relations with non-Jewish women would be impossible. Therefore, a strict legal framework was created for the inevitable relations. In other words, the Torah deemed it preferable for the relations to take place in this framework rather than outside of its laws.
A simple example will help demonstrate this concept. Assume a parent has a son who insists on staying out late on Saturday nights. The parent has tried discouraging the behavior and has even imposed consequences. But the son’s peer group stays out every Saturday night and this child cannot resist the influence of his peers. The parent may decide that he will be more effective in influencing his son’s behavior by creating boundaries than by attempting to completely arrest the behavior. If he adopts this alternative strategy, he will sit down with his son and establish some limits. Perhaps, a late curfew, or a limit on the number of Saturday nights per month the son can be out late. So, rather than continuing his attempts to completely end the behavior, the father has elected to put in place limits that will minimize the damage caused by the behavior.
Our Sages are asserting that the Torah adopted the father’s strategy of setting limits rather than attempting to completely arrest the behavior. The warrior is not forbidden from engaging in an intimate encounter with the captive but limits are set on the relationship. The relationship cannot be made permanent without preparing the prospective wife for Torah life and conversion. By this means the Torah focuses on limiting the damage caused by the behavior rather than focusing on likely fruitless attempts to completely vanquish the behavior.
3. The path to recovery after the warrior’s encounter with the Yifat Toar What is the connection between the laws in inheritance and the mitzvah of Yefat Toar? Rashi explains that the shunned wife discussed in the laws of inheritance is a Yefat Toar. In other words, the Yefat Toar will eventually be despised by the soldier who has taken her as his wife.
Why will the husband come to hate this Yefat Toar? The answer requires an understanding of human nature. We have various instincts. The mitzvah of Yefat Toar assumes that at times these desires can overcome us. At these moments we may not be able to control our behavior. However, the Torah recognized also that with time, this passion subsides and we return to our normal, more sane state of mind.
With the return of sanity we attempt to restore our self-image. We wish to see ourselves as good wholesome individuals. We do not wish to be reminded of the animalistic component of our personality or the occasions when we lost self control. To accomplish the restoration of our self-image, we must purge all memory and reminders of our previous behavior that now, we find shameful. If we are successful, we can again view ourselves as sane, good human-beings.
4. The impact on this recovery of marriage to the Yifat Toar Now, imagine a person who could not purge his conscious of a previous embarrassing lapse. This individual would be unable to completely restore a positive self-image. Surely, the individual would resent the constant reminder of downfall. The Yefat Toar is such a reminder. The presence of this wife does not allow the husband to restore his cherished positive self-image. Her very presence in his life is a reminder of his loss of control and lapse of sanity. Inevitably, he will come to resent this wife. She is a constant indication of the animalistic desires lurking just under the surface. She will become the shunned wife.
Wealth may be a Blessing or Curse
When you build a new house, you should make a fence for your roof. Do not allow a dangerous situation to exist in your house, since someone can fall. (Devarim 22:18)
1. The commandment to post a fence around one’s roof is part of a series of related commandments The Torah instructs us to remove any hazard from our home. The Torah expresses this law in reference to a flat roof. These flat roofs were used for various functions. Dwellers and others had occasion to walk on these roofs. This created a danger. A careless person could fall from the roof. In order to prevent such an accident, a fence or railing must be placed around the roof.
This mitzvah is preceded by the commandment to send away the mother bird. The next pasuk discusses the prohibition against planting mixed species in a vineyard. Is there any connection between these commandments? Rashi suggests that there is an association between these mitzvot. He explains that these mitzvot are discussed together in order to communicate a message. This message is that the performance of one mitzvah leads to the performance of another mitzvah. How is this message communicated through these passages? First, the Torah discusses the mitzvah of sending away the mother bird. Then, the mitzvah of erecting a fence around a roof is discussed. The message is that the fulfilling the mitzvah of sending away the mother bird will result in the opportunity to perform another mitzvah. This is the mitzvah of erecting a fence. The mitzvah of erecting a fence is followed by the commandment prohibiting the planting of mixed species in a vineyard. Again, the message is that the performance of one mitzvah leads to the performance of another. The erecting of the fence leads to the observance of the prohibition against planting mixed species.
2. The reward for a mitzvah is the opportunity to perform further mitzvot The simple explanation of Rashi’s comments is that the performance of one mitzvah is rewarded by the opportunity to perform another. If this is the explanation of his comments, then Rashi is not be suggesting that a person who sends away the mother bird will suddenly be rewarded by occupying a new home. The reward for performing commandments is not material enrichment. However, Rashi is suggesting that the opportunity to perform other mitzvot will arise. This opportunity is the reward.
However, this simple interpretation of Rashi is difficult to accept. First, it seems impossible to derive this lesson from these specific passages. The lesson can be derived from countless combinations of passages. Any three passages that enumerate three commandments can teach the same lesson. The performance of one commandment is rewarded with the opportunity to perform the other commandment.
Second, these three mitzvot do involve material possessions. According to Rashi, the Torah is telling that the reward for performing a mitzvah is the opportunity to perform another mitzvah. In order to communicate this message clearly, the Torah should have picked a different set of mitzvot. The Torah should have grouped a set of commandments that are not associated with the accumulation of wealth. Why did the Torah pick these specific commandments to act as the vehicle for its message? Why did the Torah choose mitzvot that are associated with wealth?
3. Mitzvot teach moderation These two questions suggest a deeper understanding of Rashi’s comments. Many of the Torah’s mitzvot regulate our involvement in the material world. These commandments establish a healthy relationship between the human being and material possessions. A person should enjoy material blessings. A person should not become absorbed in these blessings. The mitzvot mediate our relationship with our possessions.
According to Rashi, these passages are communicating that wealth can be a blessing. It can also corrupt an individual. A person who observes the mitzvot establishes an appropriate relationship with the material world. Such a person can be rewarded with greater material wealth. Wealth will not corrupt this person. This person will scrupulously observe the mitzvot that apply to these new possessions. These mitzvot will regulate the person’s relationship with these new material possessions. These passages specifically describe commandments that regulate and moderate our relationship with our material wealth. According to Rashi, the message of the series is that though observing these mitzvot we train ourselves to moderate our relationship with our material blessings. With this lesson learned, we are blessed with further wealth. Again, we are required to continue to demonstrate moderation in our relationship with these new blessings. We do this through observance of the commandments relevant to our new wealth. This prepares us for further material blessings.
4. Without mitzvot wealth may be a curse In contrast, a person that is corrupted by wealth cannot be rewarded with additional wealth. Such a reward would really be a curse. The additional wealth will only encourage the further corruption of the individual. The person will become more absorbed in the material world.
 Rabbaynu Moshe ben Maimon (Rambam / Maimonides) Mishne Torah, Hilchot Melachim 8:2.  Rabbaynu Shlomo ben Yitzchak (Rashi), Commentary on Sefer Devarim 21:11.  Rabbaynu Shlomo ben Yitzchak (Rashi), Commentary on Sefer Devarim 21:11.  Rabbaynu Shlomo ben Yitzchak (Rashi), Commentary on Sefer Devarim 22:8.