Chapter: It is permissible to perform 'Umrah during the months of Hajj
Ibn Abbas (Allah be pleased with them) reported that Allah's Messenger ( صلی اللہ علیہ وسلم ) observed the morning prayer at Dhu Tawa (a valley near Mecca) and arrived (in Mecca) when four days of Dhul-Hijja had passed and he commanded his Companions that they should change their Ihram (of Hajj) to that of Umra, except those who had brought sacrificial animals with them.
Authentic