Musannaf Ibn Abi Shayba 17:1148

Abu Bakr narrated to us, he said: Sufyan ibn ‘Uyaynah narrated to us, from Ayyub, he said: I heard Sa‘id ibn Jubayr say: We used to differ regarding things, so I wrote them down in a book. Then I came with them to Ibn ‘Umar to ask him about them secretly. If he had known about it, it would have been the decider between me and him.