In The Jewish Law of Inheritance, Dayan Dr. I Grunfeld discusses at great length the sefer Nahalah LeYisrael and its author, Rav Yisrael Moshe Hazan, the Chief Rabbi of Rome at around 1850. Dayan Grunfeld writes:
R. Hazan’s work is one of the most brilliant expositions extant of the Jewish Law of Inheritance and its underlying principals and ideas. It starts by analysing the concepts nahalah and yerushah, both philologically and conceptually. The Hebrew word נחלה (nahalah) is derived from the word נחל (nahal), which means river or stream. A nahalah or inheritance cannot be compared to either a purchase or a gift. In both cases, prior to the legal transaction, the purchaser or donee had no claim or legal relationship whatsoever to the seller or the donor or the objects of the purchase or gift. In the case of nahalah, however, the relative, who is the legal heir according to the Torah, had a claim to the estate ever since he was born. His right to the estate is an original and natural one. The expression used by the author is זכות עצמית שיש ליורשים בגוף הנכסים מעיקרא, that the inheritance is an original right (not a derivative one) which rests on the body of the estate in favour of him who is the legal heir. At the moment of death of the one who transmits the inheritance, that original right flows like a river to the one who possessed it from the beginning. The original right of the heir has always been there, though dormant, and at that moment of death of the one who transmits the inheritance to the heirs, the dormant right revives. As R. Hazan points out in his work, the legal position which is inherent in the Hebrew word נחלה can be symbolically expressed by applying to it the biblical verse כל הנחלים הולכים אל הים, all the rivers run into the sea, the ‘sea’ being the legal heir to whom the inheritance flows by a natural process as a river flows into the sea.
This is a beautiful example of a Hebrew word carrying the essence of the concept it signifies.
The comparison of the right of yerushah to the natural force of a flowing river stands in sharp contrast to the “freedom of testation,” the idea that one has the right to direct the disposition of assets upon death as he or she wishes.