Musnad Ahmad 25:1666

Rawh and Abu Dawud narrated to us—the meaning being the same—they said: Hisham ibn Abi Abd Allah narrated to us, from Qatadah, from Abu Hassan al-A’raj, from Ibn Abbas: "That the Prophet of Allah, may Allah bless him and grant him peace, prayed at Dhu al-Hulayfah. Then he marked the sacrificial animal on the right side of the hump, wiped the blood from it, and garlanded it with two sandals. Then he mounted his she-camel, and when it stood upright with him at al-Bayda’, he entered into Ihram." He said: "And he entered into Ihram at the time of Dhuhr." Abu Dawud said: "For Hajj."