The people used to consider performing Amra during the months of Hajj to be among the most sinful acts on earth. They would treat Muharram as Safar, saying, "Once the camels' backs have healed, the tracks have faded, and Safar has ended, Amra becomes lawful for whoever wishes to perform it."The Prophet ﷺ and his companions arrived on the morning of the fourth, having entered ihram for Hajj, and he ordered them to convert it into an Amra. This struck them as a serious matter, so they asked, "Messenger of Allah, what kind of release is this?"He replied, "A complete release."
كانوا يرون أن العمرة في أشهر الحج من أفجر الفجور في الأرض، ويجعلون المحرم صفرا ويقولون: إذا برأ الدبر، وعفا الأثر، وانسلخ صفر حلت العمرة لمن اعتمر فقدم النبي ﷺ وأصحابه صبيحة رابعة مهلين بالحج، فأمرهم أن يجعلوها عمرة فتعاظم ذلك عندهم فقالوا يا رسول الله، أي الحل؟ قال: حل كله.
Bukhari narrated it in the book of Hajj (1564), and Muslim narrated it in the book of Hajj (1240), both from the hadith of Wahib, who said, Ibn Tawus narrated to us, from his father, from Ibn Abbas, who mentioned it.