(Note: this is a revision and an elaboration of an earlier post from my other blog.)
The story of the Daughters of Zelophehad is one of the most fascinating legal stories in the Torah. It is divided into two parts, and the end of this story (at the very end of Numbers) is the last act Moses does in the Torah, apart from his long speech or speeches in Deuteronomy. Moses' final act is not to faithfully transmit a static set of law, but instead to modify an existing in the name of God and justice, and thereby set up up a flexible evolving common law approach to halacha.
Here's the background. Each of the 12 tribes was to own a specific region of the land, and all of the families in that tribe would own some portion of that tribe's land. The land would remain in both the tribe and family. If the land were sold, it would revert back to the family every fifty years in the Jubilee year. (Lev. 25:13, 23-24.) Since a person's tribe is determined patrilineally, the original scheme was that only males could inherit land. Thus, a father's land holdings would be passed down to his son or sons. A daughter would presumably marry and join the family of her husband. In short, the law set up a fairly conservative static system that would preserve family land holdings through male inheritance.
This was the state of the law until the daughters of Zelophehad showed up. (Num. 27:1-11.) Zelophehad was a member of the tribe of Manasseh, and he died with five daughters but no sons. Under the rules then in place, his daughters would be left with no inheritance. The daughters argued to Moses and everyone else that they should be allowed to inherent his share. "Let not our father's name be lost to his clan just because he had no son! Give us a holding among our father's kinsmen." (Num 27:4.) Moses then checked with God.
One of our midrashim (1:5:116) humorously reflects the attitudes of Talmudic times. It notes that the daughters of Zelophehad were wise and knew how to argue. They waited until Moses was elaborating on the laws of levirate marriage. They then argued that if their status is of sons, they should inherit, and if their status is of daughters, then their mother should be subject to a levirate marriage. This forceful argument prompted Moses to check with God. Sometimes, midrashim reflect more on the storyteller than then characters in the story, and this one --- with a clever separation of cases argument --- reflects a session of gemara in Talmudic times more than a discussion in the Sinai wilderness.
But let's continue with the story. Moses checked with God, and God said that the daughters were right. "The plea of Zelophehad's daughter is just." (Num. 27:5.) From now on, the rule is that if a man dies without sons but with daughters, the property should be transferred to his daughters. (If he dies without any children, there is a more complex hierarchy of inheritance.)
Another midrash (1:5:117) splits on whether Moses actually knew the law (but consulted God to avoid embarrassing the numerous other authorities who did not, or did not actually know the law because it was such a difficult case. The latter explanation seems right to me. There is no indication in the text at all that Moses might have actually known the law. Moreover, there is nothing in any earlier law that suggests that this exception for families with only daughters was in fact the law.
Thus, this was not merely an elaboration or clarification of the existing law but an entirely new rule. Before this "case" was brought, the daughters would have received nothing and Zelophehad's other relatives would have inherited land. Now the daughters inherent and the other relatives receive nothing. And the basis for this change in the law, according to God, is simply justice. "The plea of Zelophehad's Daughter's is just." (Num. 27:5.)
Accordingly, this story shows something important about the law. It evolves. The children of Israel started with one set of legal rules, but they proved to be unjust in a particular situation. God then modified the rules to comport with justice, producing a second set of rules.
It gets better. Eight chapters later, in the last chapter of Numbers, new people show up with a new problem with this law. And it changes again. (Num. 36:1-12.)
The family heads of Zelophehad's clan show up with a complaint. If the daughters of Zelophehad marry someone from another tribe, the sons for this new marriage will inherit not only their father's land holding (from the other tribe), but also the land holdings of Zelophehad (from Manasseh). So some family from another tribe will end up permanently owning land smack dab in the middle of Manasseh. The total amount of land that the people of Manasseh own will be permanently reduced.
Moses agreed with this argument and "commanded the children of Israel according to the word of the Lord, saying 'The pleas of the the tribe of the sons of Joseph is just.'" Moses then set forth a new rule: daughters may inherit under the old rule only if they marry members of their own tribe. If they marry members of a different tribe, they may not inherit. (The end of the story is that the Daughters of Zelophehad ended up marrying their uncles or cousins, and everyone lived happily ever after.)
So by this time, the law has now gone through three stages of development. The original law (only sons inherit), the modified law (daughters can inherit if there are no sons), and the modified modified law (only if they marry someone from their tribe).
Several points are worth noting here.
First, the Torah could have given us just the final rule without showing any of its intermediate forms of development. The fact that we see the evolution of the law suggests that the evolution itself is important, not just the final law.
Second, Moses used the identical language (and the Hebrew is identical: keyn) to describe the plea of the Manasseh tribe here that God used to describe the plea of the daughters of Zelophehad. Their plea is "just". (Some translations use "right".)
Third, the text does not say that Moses checked with God before stating the new rule. Instead, Moses himself spoke to the Children of Israel "al pi Adonai": according to the work of God.
Fourth, Moses changed the very law that God himself had earlier changed.
What do we make of this? I think requires people to modify halacha, even an explicit law of the Torah, so long as it is based on justice. This is not merely permitted, but it required as part of the divine methodology, "al pi Adonai".
God himself first changed the law when confronted with a just plea. Once God established this methodology, Moses was not only free, but obligated, to employ this methodology himself in response to the other litigants with a just plea. And doing so, he spoke "al pi Adonai."
This may seem like a radical notion of law. But in fact, it is exactly how Anglo-American common law works. Judges initially promulgate a set of rules, one case at a time. But over time, new situations arise that do not merely require the application of existing laws to new situations, but actually require the legal rules themselves to change in response to these new situations. But this is not a license for judges to change the law because of personal preferences or to ignore the law altogether. Under stare decisis, there is a strong presumption for leaving settled law alone. It takes a strong showing of injustice to change the common law. But when a party can make such a showing, the common law changes.
Law may start out static. But it cannot remain that way forever. The last act that Moses took in the Torah was a forward looking juridical act. He took an existing law, explicitly set forth by God, and changed it in the name of justice.