Musannaf Ibn Abi Shayba 13:1

Abu Abd al-Rahman narrated to us, he said: Abu Bakr Abdullah ibn Muhammad ibn Abi Shayba narrated to us, he said: Jarir ibn Abd al-Hamid narrated to us, from Mansur, from the companions of Ibrahim, from Ibrahim, and from al-Mughira, from Ibrahim and al-Sha'bi regarding two partners. They both said: The partnership is according to what they have agreed upon, and the loss is according to the capital.