Musnad Ahmad 28:29

Isma'il narrated to us, Yahya ibn Abi Ishaq narrated to us, 'Abdah ibn Abi Lubabah narrated to me, from Habib ibn Abi Thabit, Abu 'Abdullah, the freed slave of 'Abdullah ibn 'Amr, narrated to me: 'Abdullah ibn 'Amr ibn al-'As narrated to us while we were circumambulating the House (the Ka'bah), he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There are no days in which deeds are more beloved to Allah than these days." It was said: Not even Jihad in the way of Allah? He said: "Not even Jihad in the way of Allah, except for a man who goes out with his self and his wealth, then does not return with anything of them until his lifeblood is shed." He said: So I met Habib ibn Abi Thabit and asked him about this Hadith, and he narrated to me something similar to this Hadith. He said: And 'Abdah said: They are the ten days.