Musannaf Ibn Abi Shayba 26:324

'Abbad ibn al-'Awwam narrated to us, from Muhammad ibn Salim, from Ibrahim and al-Sha'bi, that he heard them both explaining their saying: "They inherit from one another." They said: "If one of them died and left behind wealth, and the other left nothing, the heirs of the one who left nothing would inherit the inheritance of the owner of the wealth, and the heirs of the owner of the wealth would have nothing."