Musnad Ahmad 25:503

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, who said: Abdullah ibn Tawus narrated to me, from his father, from Ibn Abbas, who said: "The Messenger of Allah, peace and blessings of Allah be upon him, did not have Aisha perform 'Umrah on the night of al-Hasbah except to cut off the affair of the people of polytheism. For they used to say: 'When the sore heals, the track is erased, and Safar enters, then 'Umrah has become permissible for the one who performs 'Umrah.'"