Mawlid is not permitted in the Koran. There is no any ayat that Allah is saying/commanding/authorizing people "muham-madans" to celebrate the birthday of Marehemu Muham-mad.
The Prophet said, "He who innovates something in this matter of ours that is not of it will have it rejected." He also said, "Beware of innovations, for every innovation (kul bida`) is misguidance."
The word every (kul) is a term of generalization, including all types of innovations, with no exception, and that therefore, celebrating Mawlid is misguidance.