Halakhah for Bava Batra 8:5
הָאוֹמֵר אִישׁ פְּלוֹנִי בְנִי בְּכוֹר לֹא יִטֹּל פִּי שְׁנַיִם, אִישׁ פְּלוֹנִי בְנִי לֹא יִירַשׁ עִם אֶחָיו, לֹא אָמַר כְּלוּם, שֶׁהִתְנָה עַל מַה שֶּׁכָּתוּב בַּתּוֹרָה. הַמְחַלֵּק נְכָסָיו לְבָנָיו עַל פִּיו, רִבָּה לְאֶחָד וּמִעֵט לְאֶחָד וְהִשְׁוָה לָהֶן אֶת הַבְּכוֹר, דְּבָרָיו קַיָּמִין. וְאִם אָמַר מִשּׁוּם יְרֻשָּׁה, לֹא אָמַר כְּלוּם. כָּתַב בֵּין בַּתְּחִלָּה בֵּין בָּאֶמְצַע בֵּין בַּסּוֹף מִשּׁוּם מַתָּנָה, דְּבָרָיו קַיָּמִין. הָאוֹמֵר אִישׁ פְּלוֹנִי יִירָשֵׁנִי בִּמְקוֹם שֶׁיֵשׁ בַּת, בִּתִּי תִירָשֵׁנִי בִּמְקוֹם שֶׁיֶּשׁ בֵּן, לֹא אָמַר כְּלוּם, שֶׁהִתְנָה עַל מַה שֶּׁכָּתוּב בַּתּוֹרָה. רַבִּי יוֹחָנָן בֶּן בְּרוֹקָה אוֹמֵר, אִם אָמַר עַל מִי שֶׁהוּא רָאוּי לְיָרְשׁוֹ, דְּבָרָיו קַיָּמִין. וְעַל מִי שֶׁאֵין רָאוּי לְיָרְשׁוֹ, אֵין דְּבָרָיו קַיָּמִין. הַכּוֹתֵב אֶת נְכָסָיו לַאֲחֵרִים וְהִנִּיחַ אֶת בָּנָיו, מַה שֶּׁעָשָׂה עָשׂוּי, אֲבָל אֵין רוּחַ חֲכָמִים נוֹחָה הֵימֶנּוּ. רַבָּן שִׁמְעוֹן בֶּן גַּמְלִיאֵל אוֹמֵר, אִם לֹא הָיוּ בָנָיו נוֹהֲגִין כַּשּׁוּרָה, זָכוּר לְטוֹב:
If one says: "This man, my son, a bechor, shall not take a double portion," or "This man, my son, shall not inherit with his brothers," he has said nothing, for he stipulates against what is written in the Torah. [And he cannot divest him of the inheritance unless he gives his property as a gift to his other sons.] If one distributed his property among his sons by his word, [one's command in the face of death being regarded as "written and transmitted in the Torah," and not requiring a kinyan (an act effecting acquisition), (this being the thrust of "by his word")] and he accorded more to one and less to another, and made the bechor equal to them [by using an expression of "gift"], his words stand. [And this is not considered stipulating against what is written in the Torah. For one has the right to give his money as a gift to whomever he wishes.] And if he said "as inheritance," [i.e., If he gave more to one and less to another as inheritance, saying: "This man, my son, shall inherit a field of a beth-kor, and that man, my son, shall inherit a field of a beth-lethech," or of his son, a bechor, that he is to inherit equally with the others, he has said nothing, having stipulated against what is written in the Torah]. If he wrote "as a gift" either in the beginning, the middle, or the end, his words stand. [in the beginning: "Let this field be given to this one and let him inherit it." in the end: "Let him inherit it and let it be given to him." in the middle: "Let him inherit this field, and let it be given to him, and let him inherit it."] If one says: "Let this man inherit me," where he has a daughter, or "Let my daughter inherit me," where he has a son, he has said nothing, having stipulated against what is written in the Torah. R. Yochanan b. B'roka says: If he says this about one who is fit to inherit him, his words stand. And if about one who is not fit to inherit him, his words do not stand. [e.g., If he said it about one son among the other sons, or about one daughter among the other daughters, his words stand, it being written (Deuteronomy 21:16): "Then it shall be, on the day that he causes his sons to inherit" — The Torah granted the father authority to cause whichever of his sons he wishes, to inherit him. And R. Yochanan concedes that with a brother, where he has a daughter, or with a daughter, where he has a son, he has said nothing. For a daughter is not fit to inherit where there is a son; or a brother, where there is a daughter. Likewise, R. Yochanan concedes that if he made the bechor equal to the other brothers, he has said nothing, it being written (Ibid.): "He shall not be able to grant primogeniture, etc." The halachah is in accordance with R. Yochanan b. B'roka.] If one writes his property over to others, passing over his children, what he did is done, but the sages do not look favorably upon it, [even if his children to not deport themselves properly, for good children might issue from them.] R. Shimon b. Gamliel says: If his children did not deport themselves properly (and he disinherited them thus), he is "remembered for the good." [The halachah is not in accordance with R. Shimon b. Gamliel.]