Musnad Ahmad 1167:6

Muhammad ibn Fudayl narrated to us, he said: Yazid—meaning ibn Abi Ziyad—narrated to us, from Mujahid, who said: Abdullah ibn al-Zubayr said: "Perform Hajj alone (as Hajj al-Ifrad), and leave the saying of this one," meaning Ibn Abbas. So Ibn Abbas said: "Will you not ask your mother about this?" He sent to her, and she said: "Ibn Abbas spoke the truth. We went out with the Messenger of Allah, peace and blessings of Allah be upon him, as pilgrims, and he commanded us, so we turned it into an Umrah. Thus, the lawful things became permissible for us, until the incense burners were wafting between the women and the men."