O People, the deniers of Allah’s power indulge in tampering with the calendar in order to make permissible that which Allah forbade, and to forbid that which Allah has made permissible. The time has now returned to the position as it was when Allah created the heavens and the earth with a year of twelve months. Four of them are sacred: Dhu al-Qa'dah, Dhu al-Hijjah, and Muharram; and Rajab, which lies between Jumada' and Sha'ban.
(Farewell Khutbah).