Halacha

הלכה א
אֵין אָדָם יָכוֹל לְהוֹרִישׁ לְמִי שֶׁאֵינוֹ רָאוּי לְיָרְשׁוֹ וְלֹא לַעֲקֹר הַיְרֻשָּׁה מִן הַיּוֹרֵשׁ אַף עַל פִּי שֶׁזֶּה מָמוֹן הוּא. לְפִי שֶׁנֶּאֱמַר בְּפָרָשַׁת נְחָלוֹת (במדבר כז יא) "וְהָיְתָה לִבְנֵי יִשְׂרָאֵל לְחֻקַּת מִשְׁפָּט" לוֹמַר שֶׁחֻקָּה זוֹ לֹא נִשְׁתַּנָּה וְאֵין הַתְּנַאי מוֹעִיל בָּהּ. בֵּין שֶׁצִּוָּה וְהוּא בָּרִיא בֵּין שֶׁהָיָה שְׁכִיב מֵרַע בֵּין עַל פֶּה בֵּין בִּכְתָב אֵינוֹ מוֹעִיל:
כסף משנה
1.
Although all that is involved is money, a person may not give property as an inheritance to a person who is not fit to inherit, nor may he exclude a rightful heir from inheriting. This is derived from the verse in the passage concerning inheritance, Numbers 27:11: "And it shall be for the children of Israel as a statute of judgment."
This verse implies that this statute will never change, and no stipulation can be made with regard to it. Whether a person made statements while he was healthy or on his deathbed, whether orally or in writing, they are of no consequence.

הלכה ב
לְפִיכָךְ הָאוֹמֵר אִישׁ פְּלוֹנִי בְּנִי בְּכוֹרִי לֹא יִטּל פִּי שְׁנַיִם. אִישׁ פְּלוֹנִי בְּנִי לֹא יִירַשׁ עִם אֶחָיו. לֹא אָמַר כְּלוּם. אִישׁ פְּלוֹנִי יִירָשֵׁנִי בְּמָקוֹם שֶׁיֵּשׁ לוֹ בַּת. בִּתִּי תִּירָשֵׁנִי בְּמָקוֹם שֶׁיֵּשׁ לוֹ בֵּן. לֹא אָמַר כְּלוּם. וְכֵן כָּל כַּיּוֹצֵא בָּזֶה. אֲבָל הָיוּ לוֹ יוֹרְשִׁין רַבִּים כְּגוֹן בָּנִים רַבִּים אוֹ אַחִים אוֹ בָּנוֹת וְאָמַר כְּשֶׁהוּא שְׁכִיב מֵרַע פְּלוֹנִי אָחִי יִירָשֵׁנִי מִכְּלַל אֶחַי אוֹ בִּתִּי פְּלוֹנִית תִּירָשֵׁנִי מִכְּלַל בְּנוֹתַי דְּבָרָיו קַיָּמִין בֵּין שֶׁאָמַר עַל פֶּה בֵּין שֶׁכָּתַב בִּכְתָב. אֲבָל אִם אָמַר פְּלוֹנִי בְּנִי יִירָשֵׁנִי לְבַדּוֹ אִם אָמַר עַל פֶּה דְּבָרָיו קַיָּמִין. אֲבָל אִם כָּתַב כָּל נְכָסָיו לִבְנוֹ לֹא עָשָׂהוּ אֶלָּא אַפּוֹטְרוֹפּוֹס כְּמוֹ שֶׁבֵּאַרְנוּ:
כסף משנה
2.
Therefore, if a person states: "So-and-so is my firstborn son, he should not receive a double portion," or "My son so-and-so should not inherit my estate together with his brothers," his statements are of no consequence. Similarly, if he says: "Let so-and-so inherit my estate" when the dying man has a daughter, or "Let my daughter inherit my estate" when he has a son, his statements are of no consequence. Similar laws apply in all analogous situations.
If, however, he had many heirs - e.g., many sons, brothers, or many daughters - and he says while on his deathbed: "Of all my brothers, only my brother so-and-so should inherit my estate," or "Of all my daughters, only my daughter so-and-so should inherit my estate," his words are binding. This applies whether he made these statements orally or in writing.
If, however, he states: "My son so-and-so should be my sole heir," different rules apply]. If he made this statement orally, his words are binding. If, however, he had a document composed stating that his entire estate should be given to one son, he is considered merely to have appointed him as a guardian, as explained.

הלכה ג
אָמַר פְּלוֹנִי בְּנִי יִירַשׁ חֲצִי נְכָסַי וּשְׁאָר בָּנַי הַחֵצִי דְּבָרָיו קַיָּמִין. אֲבָל אִם אָמַר הַבְּכוֹר יִירַשׁ כַּפָּשׁוּט אוֹ שֶׁאָמַר לֹא יִירַשׁ פִּי שְׁנַיִם עִם אֶחָיו לֹא אָמַר כְּלוּם שֶׁנֶּאֱמַר (דברים כא טז) "לֹא יוּכַל לְבַכֵּר אֶת בֶּן הָאֲהוּבָה עַל פְּנֵי בֶן הַשְּׂנוּאָה הַבְּכֹר" (דברים כא יז) "כִּי אֶת הַבְּכֹר בֶּן הַשְּׂנוּאָה יַכִּיר":
כסף משנה
3.
If a person states: "So-and-so my son should inherit half my estate and my other sons should inherit the other half," his words are binding. If, however, he states: "My firstborn should inherit as an ordinary son," or "My firstborn should not receive a double portion among his brothers," his words are of no consequence. This is derived from Deuteronomy 21:16-17: "He cannot give the firstborn rights to the son of the beloved instead of the firstborn, the son of the hated. Instead, he shall recognize the firstborn, the son of the hated."i4

הלכה ד
וְאִם הָיָה בָּרִיא אֵינוֹ יָכוֹל לְהוֹסִיף וְלֹא לִגְרֹעַ לֹא לַבְּכוֹר וְלֹא לְאֶחָד מִשְּׁאָר הַיּוֹרְשִׁין:
כסף משנה
4.
If the person desiring to bequeath his estate was healthy, he may not increase or decrease either the portion of the firstborn or that of any other heirs.

הלכה ה
בַּמֶּה דְּבָרִים אֲמוּרִים כְּשֶׁאָמַר בִּלְשׁוֹן יְרֻשָּׁה. אֲבָל אִם נָתַן מַתָּנָה דְּבָרָיו קַיָּמִין. לְפִיכָךְ הַמְחַלֵּק נְכָסָיו עַל פִּיו לְבָנָיו כְּשֶׁהוּא שְׁכִיב מֵרַע רִבָּה לְאֶחָד וּמִעֵט לְאֶחָד וְהִשְׁוָה לָהֶן הַבְּכוֹר דְּבָרָיו קַיָּמִין. וְאִם אָמַר מִשּׁוּם יְרֻשָּׁה לֹא אָמַר כְּלוּם:
כסף משנה
5.
When does the above apply? When the person making the bequest uses the expression "inherit." If, however, he gives a present, his statements are binding.
Accordingly, when a person apportions his estate verbally to his sons on his deathbed, his statements are binding even though he gave a greater portion to one, reduced the portion of another and equated the portion of the firstborn with that of his other sons. If, however, he used wording that speaks of "inheritance," his statements are of no consequence.

הלכה ו
כָּתַב בֵּין בַּתְּחִלָּה בֵּין בָּאֶמְצַע בֵּין בַּסּוֹף מִשּׁוּם מַתָּנָה אַף עַל פִּי שֶׁהִזְכִּיר לְשׁוֹן יְרֻשָּׁה בַּתְּחִלָּה וּבַסּוֹף דְּבָרָיו קַיָּמִין. כֵּיצַד. תִּנָּתֵן שָׂדֶה פְּלוֹנִי לִפְלוֹנִי בְּנִי וְיִירָשֶׁנָּה. אוֹ שֶׁאָמַר יִירָשֶׁנָּה וְתִנָּתֵן לוֹ וְיִירָשֶׁנָּה. אוֹ יִירָשֶׁנָּה וְתִנָּתֵן לוֹ. הוֹאִיל וְיֵשׁ שָׁם לְשׁוֹן מַתָּנָה אַף עַל פִּי שֶׁהִזְכִּיר לְשׁוֹן יְרֻשָּׁה בַּתְּחִלָּה וּבַסּוֹף דְּבָרָיו קַיָּמִין. וְכֵן אִם הָיוּ שָׁלֹשׁ שָׂדוֹת לִשְׁלֹשָׁה יוֹרְשִׁין וְאָמַר יִירַשׁ פְּלוֹנִי שָׂדֶה פְּלוֹנִית וְתִנָּתֵן לִפְלוֹנִי שָׂדֶה פְּלוֹנִית וְיִירַשׁ פְּלוֹנִי שָׂדֶה פְּלוֹנִית קָנוּ. אַף עַל פִּי שֶׁזֶּה שֶׁאָמַר לוֹ בִּלְשׁוֹן יְרֻשָּׁה אֵינוֹ זֶה שֶׁאָמַר לוֹ בִּלְשׁוֹן מַתָּנָה. וְהוּא שֶׁלֹּא יִשְׁהֶה בֵּין אֲמִירָה לַאֲמִירָה כְּדֵי דִּבּוּר. אֲבָל אִם שָׁהָה צָרִיךְ שֶׁיְּהֵא לְשׁוֹן הַמַּתָּנָה מְעֹרָב בִּשְׁלָשְׁתָּן:
כסף משנה
6.
If, when apportioning his estate, a person wrote that he is giving his estate as a present, whether at the beginning, the middle, or the end, his statement is binding even though he also spoke of an inheritance.
What is implied? The person said: "Have this-and-this field given to so-and-so, my son, and let him inherit it," "Let him inherit this-and-this field, have it given to him and let him inherit it," or "Let him inherit it and have it given to him." Since he mentioned a present, even though he spoke of an inheritance at the beginning and/or at the end of his statements, his words are binding.
Similarly, if he was apportioning three fields to three different heirs, and he said: "May so-and-so inherit this-and-this field. This-and-this field should be given to so-and-so, and so-and-so should inherit this-and-this field," the intended recipients acquire the gifts even though wording indicating an inheritance was used with regard to one individual, and wording indicating a present was used with regard to another.
This applies provided that the person making the bequest did not make a significant pause between his statements. If, however, he paused, he must mention giving a present with regard to all three individuals.

הלכה ז
כֵּיצַד. אִם הָיָה לְשׁוֹן הַמַּתָּנָה בָּאֶמְצַע יֹאמַר פְּלוֹנִי וּפְלוֹנִי יִירְשׁוּ שָׂדֶה פְּלוֹנִי וּפְלוֹנִי שֶׁנְּתַתִּים לָהֶן בְּמַתָּנָה וְיִירָשׁוּם. וְאִם הָיָה לְשׁוֹן הַמַּתָּנָה בַּתְּחִלָּה יֹאמַר תִּנָּתֵן שָׂדֶה פְּלוֹנִי וּפְלוֹנִי לִפְלוֹנִי וּפְלוֹנִי וְיִירָשׁוּם. וְאִם הָיָה לְשׁוֹן הַמַּתָּנָה בַּסּוֹף יֹאמַר יִירַשׁ פְּלוֹנִי וּפְלוֹנִי (וּפְלוֹנִי) שָׂדֶה פְּלוֹנִי וּפְלוֹנִי (וּפְלוֹנִי) שֶּׁנְּתַתִּים לָהֶן בְּמַתָּנָה:
כסף משנה
7.
What is implied? If the wording mentioning a present was in the middle, he should say: "So-and-so, so-and-so, and so-and-so, should inherit this-and-this field, this-and-this field, and this-and-this field that I gave them as a present, and they should inherit it."
If the wording mentioning a present was in the beginning, he should say: "May this-and-this field, this-and-this field, and this-and-this field be given to so-and-so, so-and-so, and so-and-so, and they should inherit it."
If the wording mentioning a present was at the end, he should say: "May so-and-so, so-and-so, and so-and-so, inherit this-and-this field, this-and-this field, and this-and-this field that I gave to them as a present."

הלכה ח
יְרֻשַּׁת הַבַּעַל אַף עַל פִּי שֶׁהִיא מִדִּבְרֵיהֶם עָשׂוּ חִזּוּק לְדִבְרֵיהֶם כְּשֶׁל תּוֹרָה. וְאֵין הַתְּנַאי מוֹעִיל בָּהּ אֶלָּא אִם כֵּן הִתְנָה עִמָּהּ כְּשֶׁהִיא אֲרוּסָה כְּמוֹ שֶׁבֵּאַרְנוּ בְּהִלְכוֹת אִישׁוּת:
כסף משנה
8.
Although a husband's right to inherit his wife's estate is a Rabbinic decree, our Sages reinforced their words and gave them the strength of Scriptural Law. Hence, a stipulation in which the husband waives his right to her inheritance is not effective unless he made this stipulation while the woman was consecrated, as we have explained in Hilchot Ishut.

הלכה ט
הָעַכּוּ''ם יוֹרֵשׁ אֶת אָבִיו דְּבַר תּוֹרָה. אֲבָל שְׁאָר יְרֻשּׁוֹתֵיהֶן מַנִּיחִין אוֹתוֹ לְפִי מִנְהָגָם:
כסף משנה
9.
According to Scriptural Law, a gentile inherits his father's estate. With regard to other inheritances, we allow them to follow their own customs.

הלכה י
וְהַגֵּר אֵינוֹ יוֹרֵשׁ אֶת אָבִיו הָעַכּוּ''ם אֶלָּא מִדִּבְרֵיהֶם תִּקְּנוּ לוֹ שֶׁיִּירַשׁ כְּשֶׁהָיָה שֶׁמָּא יַחְזֹר לְמִרְדּוֹ. וְיֵרָאֶה לִי שֶׁתְּנַאי מוֹעִיל בִּירֻשָּׁה זוֹ הוֹאִיל וְאֵין הָעַכּוּ''ם מְחֻיָּב לַעֲמֹד בְּתַקָּנַת חֲכָמִים. וְאֵין הָעַכּוּ''ם יוֹרֵשׁ אֶת אָבִיו הַגֵּר וְלֹא גֵּר יוֹרֵשׁ אֶת גֵּר לֹא מִדִּבְרֵי תּוֹרָה וְלֹא מִדִּבְרֵי סוֹפְרִים:
כסף משנה
10.
A convert does not inherit the estate of his father, a gentile. Nevertheless, our Sages ordained that he be able to inherit the estate as he was entitled previously, lest he return to rebellion against God.
It appears to me that a stipulation can be made with regard to this inheritance, for a gentile is not obligated to accept our Sages' ordinances.
A gentile does not inherit the estate of his father, a convert, nor does one convert inherit another convert's estate, neither according to Scriptural Law nor according to Rabbinic Law.

הלכה יא
כָּל הַנּוֹתֵן נְכָסָיו לַאֲחֵרִים וְהִנִּיחַ הַיּוֹרְשִׁין. אַף עַל פִּי שֶׁאֵין הַיּוֹרְשִׁין נוֹהֲגִין (בּוֹ) כַּשּׁוּרָה אֵין רוּחַ חֲכָמִים נוֹחָה הֵימֶנּוּ. וְזָכוּ הָאֲחֵרִים בְּכָל מַה שֶּׁנָּתַן לָהֶן. מִדַּת חֲסִידוּת הִיא שֶׁלֹּא יָעִיד אָדָם חָסִיד בְּצַוָּאָה שֶׁמַּעֲבִירִין בּוֹ הַיְרֻשָּׁה מִן הַיּוֹרֵשׁ אֲפִלּוּ מִבֵּן שֶׁאֵינוֹ נוֹהֵג כַּשּׁוּרָה לְאָחִיו חָכָם וְנוֹהֵג כַּשּׁוּרָה:
כסף משנה
11.
Our Sages did not derive satisfaction from a person who gives his property to others, taking it away from his heirs. This applies even when the heirs do not conduct themselves properly toward him. Nevertheless, the recipients acquire everything that was given to them.
It is an attribute of piety for a pious person not to act as a witness with regard to a will in which property is being taken from an heir. This applies even when the property is being taken from a son who does not conduct himself properly, and being given to a brother who is wise and who conducts himself properly.

הלכה יב
יִשְׂרָאֵל שֶׁהֵמִיר יוֹרֵשׁ אֶת קְרוֹבָיו הַיִּשְׂרְאֵלִים כְּשֶׁהָיָה. וְאִם רָאוּ בֵּית דִּין לְאַבֵּד אֶת מָמוֹנוֹ וּלְקָנְסוֹ שֶׁלֹּא יִירַשׁ כְּדֵי שֶׁלֹּא לְחַזֵּק אֶת יְדֵיהֶם הָרְשׁוּת בְּיָדָן. וְאִם יֵשׁ לוֹ בָּנִים בְּיִשְׂרָאֵל תִּנָּתֵן יְרֻשַּׁת אֲבִיהֶן הַמּוּמָר לָהֶן. וְכֵן הַמִּנְהָג תָּמִיד בַּמַּעֲרָב:
כסף משנה
12.
Although a Jew converts out of the faith, he retains the right to inherit the estates of his Jewish relatives as before. If, however, the court sees fit to make him forfeit his money and penalize him by preventing him from receiving the inheritance so as not to strengthen his hand, they have that power. If he has children " among the Jewish people, the inheritance due their father, the apostate, should be given to them. This is the custom that is always followed in the West.

הלכה יג
צִוּוּ חֲכָמִים שֶׁלֹּא יְשַׁנֶּה אָדָם בֵּין הַבָּנִים בְּחַיָּיו אֲפִלּוּ בְּדָבָר מוּעָט שֶׁלֹּא יָבוֹאוּ לִידֵי תַּחֲרוּת וְקִנְאָה כַּאֲחֵי יוֹסֵף עִם יוֹסֵף:
כסף משנה
13.
Our Sages commanded that a person should not differentiate between his children in his lifetime, even with regard to a small matter, lest this spawn competition and envy as happened with Joseph and his brothers.

משפטים הלכות נחלות פרק ו
Mishpatim Nahalos Chapter 6