Commentary for Kiddushin 34:19

והתניא רוח חכמים נוחה הימנו לא קשיא כאן שהורתו ולידתו שלא בקדושה

But once they<span class="x" onmousemove="('comment',' Sc. the idols or the wine.');">²⁵</span> have come into the proselyte's possession, this [exchange] is forbidden.<span class="x" onmousemove="('comment',' Because one may not benefit from these in any way.');">²⁶</span> Now, should you think that [the proselyte succeeds] by Biblical law, even if they have not yet come into his possession, when he takes [the money or the produce], he takes something in exchange for an idol!<span class="x" onmousemove="('comment',' For if he inherits by Biblical law, he automatically has a half-share in everything, whether he has taken possession or not.');">²⁷</span> Hence it [his succession] is [only] by Rabbinical law, the Rabbis having enacted a preventive measure, lest he return to his evil ways.<span class="x" onmousemove="('comment',' For the sake of the estate. - The reason that he cannot succeed by Biblical law is that 'a proselyte is as a new-born babe,' who has no kinsmanship whatsoever with any of his pre-conversion relations.');">²⁸</span> It has been taught likewise: When was this said? If they inherited [the property]. But if they went into partnership,<span class="x" onmousemove="('comment',' In a business, or in property, among which were idols and forbidden wine.');">²⁹</span> it is forbidden.<span class="x" onmousemove="('comment',' Which proves that he does not inherit by Biblical law, for in that case it would be partnership.');">³⁰</span> A heathen [succeeds] a proselyte, or a proselyte [succeeds] a proselyte, neither by Biblical law nor by the law of the Soferim. For we learnt:<span class="x" onmousemove="('comment',' [This is no Mishnah, hence Var. lec. 'it has been taught'.]');">³¹</span> If a man borrows money from a proselyte whose children were converted together with him, he must not return it to his children,<span class="x" onmousemove="('comment',' Because they are not his heirs.');">³²</span> and if he does, the spirit of the Sages is not pleased with him. But it was taught:<span class="x" onmousemove="('comment',' [This is a Mishnah, Sheb. X, 9, hence Var. lec., 'we learnt'.]');">³³</span> The spirit of the Sages is pleased with him? - There is no difficulty. The former refers to where his [sc. the child's] conception and birth were not In sanctity:<span class="x" onmousemove="('comment',' I.e., before the father's conversion. If the debtor returns the money to his child, he ipso facto recognises him as heir against the desire of the Rabbis, who held that there is absolutely no relationship between them.');">³⁴</span>

Daf Shevui to Kiddushin