Musnad Ahmad 28:610

Azhar ibn al-Qasim narrated to us, al-Muthanna—meaning ibn Sa'id—narrated to us, from Qatadah, from 'Abdullah ibn Baba, from 'Abdullah ibn 'Amr ibn al-'As, that the Prophet, peace and blessings of Allah be upon him, used to say: "Indeed, Allah, the Almighty and Majestic, boasts to His angels on the evening of 'Arafah about the people of 'Arafah. He says: 'Look at My servants; they have come to Me disheveled and dusty.'"