Quotation for Bava Batra 266:3

ויתן אברהם את כל אשר לו ליצחק, “Avraham gave all that was his to Yitzchok.” How could he have done so, seeing that the Talmud in tractate Baba batra folio 133 denies a father the right to transfer his estate even from a unworthy son to a worthy son, the reason being that the son from whom his potential inheritance is taken away may have a worthy son himself, whereas the son to whom it has been transferred may have an unworthy son. (Compare Talmud tractate Pessachim 49) We read in Job 27,17 concerning the definition of a righteous person that יכין וצדיק ילבש וכסף נקי יחלק, “the just will put it on, and the innocent shall divide the silver.” [The problem is how could Avraham disinherit his firstborn son Yishmael legally? Ed.] It is especially puzzling since according to the Talmud in tractate Yuma folio 28, credits him with even having observed Rabbinic ordinances, such as certain procedures for preparing food when a festival day is followed by the Sabbath when preparing food is forbidden. We have to conclude that both Avraham and Yishmael were actually converts, neither having been born as Jews. Converts do not legally inherit their fellow converts, neither by Biblical law nor by Rabbinic decree. (Talmud tractate Kidushin folio 17). Rabbeinu Chananel bar Sh’muel suggests that Avraham gave all he had to Yitzchok before the sons of Keturah had been born, This is indicated by this having been reported already in Genesis 24,36: where he is reported immediately after Sarah having given birth to him as receiving all of his father’s estate. [Seeing that Yishmael, as Hagar’s son was the son of a slave woman, he could not legally own anything that had been Avraham’s or Sarah’s as slaves do not own their master’s or their mistress’ property. So where was the problem? Ed.]