SHAFAQNA – When the Islamic army reached near Mecca, Saad ibn Ibadah who was carrying the flag of the Islamic forces recited the following poem: Today is the day of combat, today your lives and your wealth is Halal, today is the day of suffering for Quraysh (the tribe controlling Mecca). The Prophet of Islam (PBUH) became very upset by hearing these words, and to prevent despair and disappointment among people of Mecca, said immediately: Today is the day of mercy, today is the day of dignity for Quraysh, today is the day when God granted grandeur to Mecca. Then Saad was dismissed from his position, and Imam Ali (AS) was appointed in his place by the Prophet (PBUH). Eventually the Islamic army entered Mecca with the slogan of mercy whilst Imam Ali (AS) holding the flag .
 Seerah ibn Hisham, Vol. 4, page 49.