مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2352
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn ‘Abbas (رضي الله عنه) said: The Messenger of Allah (ﷺ) did not allow ‘A’ishah to do 'Umrah on the night of al-Hasbah [when the pilgrims come to Muhassab after leaving Mina on Yaumut-Tarwiyah (8th Dhul-Hijjah)] in order to put an end to the custom of the mushrikeen, because they used to say: When the backs of the camels have healed, the tracks of the pilgrims have been erased and the month of Safar has begun, then it becomes permissible to do ‘Umrah for anyone who wants to do it.
Musnad Ahmad 2361A saheeh hadeeth; this is a hasan isnad]