Musannaf Ibn Abi Shayba 7:244

Mu'tamir ibn Sulayman narrated to us, from Kathir ibn Nabata, that he heard him narrating that there were two brothers who were partners, and one of them wanted to separate from his brother. A slave of his said, "He is free or emancipated if he does not separate from his brother," and his mother ordered him to separate from his brother. He asked al-Hasan, or he was asked while he was listening to that, and he said: "Let him offer expiation for his oath, and let him maintain ties of kinship; let him remain partners with his brother," or as he said. Abu al-'Ala' Kathir said: So he narrated it to al-Hakam ibn Aban, and he said: "This is the opinion of Tawus."