All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Celebrating the birthday of the Prophet, sallallaahu ‘alayhi wa sallam, or anyone’s birthday was not a practice of the Prophet, sallallaahu ‘alayhi wa sallam, or his Companions. It is indisputably established that acts of worship are to be learned only from the Quran and Sunnah (tradition). It is also established that Sharee‘ah (Islamic legislation) is what has been ordained by Allaah The Almighty and by the Prophet, sallallaahu ‘alayhi wa sallam. Likewise, any act of worship which the Prophet, sallallaahu ‘alayhi wa sallam, did not observe -- although there could have been a motive for it and there was no reason why he did not do it -- but a person insists on doing it, is considered a detestable Bid‘ah (religious innovation) which must be avoided. This is the most accurate criterion for defining Bid‘ah.
Let us apply this definitive criterion to the act of celebrating the birthday of the Prophet, sallallaahu ‘alayhi wa sallam. The existing motives were the love of Muslims for the Prophet, sallallaahu ‘alayhi wa sallam, the desire to thank Allaah The Almighty for his birth, and the wish to show the disbelievers, the Jews and Christians how much he was loved, during the time of the Prophet, sallallaahu ‘alayhi wa sallam, and the Companions. There were no reasons why such a celebration was not made, as soon after this time they conquered and fought the disbelievers, who used to glorify their leaders and celebrate their birthdays. Despite all this, the Prophet's birthday was not celebrated during that time. This means that celebrating it now is an innovation.
On the other hand, reminding people of the biography of the Prophet, sallallaahu ‘alayhi wa sallam, can be achieved by teaching, explaining and discussing it in mosques, schools and universities. It is not proper to relate all of it in an hour or a night, to chant it while music is played, or to commit acts which contradict monotheism, which is the core of the message of the Prophet, sallallaahu ‘alayhi wa sallam. Seeking relief from a being other than Allaah The Almighty, such as the Prophet or a righteous person is wrong. May Allaah The Almighty help us avoid religious innovations.