Musannaf Ibn Abi Shayba 13:3324

Abu Bakr narrated to us, he said: Abbad ibn al-Awwam narrated to us, from Umar ibn Amir, from Qatadah, from Nafi, from Ibn Umar, regarding a man who hired a worker, then he hired him out for more than what he had hired him for. He said: The surplus belongs to the first [hirer].