Ibn Hibban

Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) performed four Umrahs, all of which were in the month of Dhu al-Qi'dah. One Umrah was performed from Hudaybiyyah, which was in the month of Dhu al-Qi'dah. The second was performed in the following year, also in Dhu al-Qi'dah. One Umrah was performed from Ji'ranah when he distributed the spoils of the Battle of Hunayn, and this too was in Dhu al-Qi'dah. One Umrah he performed along with Hajj.

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates: By Allah! The Messenger of Allah did not perform Umrah in the month of Dhul-Hijjah so that he could end the tradition of the polytheists through it. The reason for this is that the Quraysh and the followers of their religion used to say: When the camel's hair grows long and the wound on its back heals (i.e., the wound that is caused by placing the saddle for the pilgrim), and the month of Safar begins, then it becomes permissible for the one performing Umrah to do so. They used to declare performing Umrah in the month of Dhul-Hijjah as forbidden, so the Prophet (peace and blessings be upon him) had Lady Aisha (may Allah be pleased with her) perform Umrah for this very reason, to oppose their statement.