Musannaf Ibn Abi Shayba 26:335

Ali ibn Mushir narrated to us, from Sa’id, from Qatadah, from Jabir ibn Zayd and al-Hasan regarding the hermaphrodite (al-khuntha). They both said: "He is inherited from [based on] his urination." Qatadah said: "So I wrote regarding that to Sa’id ibn al-Musayyib, and he said: 'Yes, and if he urinates from both of them together, then [it is determined by] whichever of them precedes.'"