Musannaf Ibn Abi Shayba 3:5805

Ibn ‘Uyaynah narrated to us, from al-Zuhri, from ‘Urwah, from ‘A’ishah, that the prayer, when it was first made obligatory, was two rak‘ahs. Then it was increased in the prayer of residence, and it was kept as it was in the prayer of travel. I said to ‘Urwah, "What is the matter with ‘A’ishah? She used to complete the prayer [four rak‘ahs] during travel, while she says this [hadith]." He said, "She interpreted it as ‘Uthman interpreted it." I did not ask him what ‘Uthman interpreted.