פירוש על קידושין 34:15

A Jew cannot derive benefit from idols or non-Jewish wine. Therefore, once the convert actually takes possession of his father’s inheritance, it would be prohibited to exchange them for other parts of the inheritance. This would be considered deriving benefit. But he can exchange them before he takes possession because he does not yet own them. This proves that the convert does not inherit from his non-Jewish father from biblical law, because if he did, then as soon as his father died the son would be considered as if he owned the idols or wine and he would not be able to exchange them.