Q: Some of our Muslim brethren hold birthday parties for themselves and their children, what is the ruling on such festivals?
A: The basic principle regarding acts of Ibadah (worship) is that they are Tawqifiy (bound by a religious text and not amenable to personal opinion), and as such, no one is allowed to worship Allah in a way other than which He ordained, because the Prophet (peace be upon him) said in the Sahih (authentic) Hadith:
Anyone who introduces anything into this matter of ours (Islam) that is not part of it will have it rejected. 
He (peace be upon him) also said:
Anyone who does an action which is not in accordance with this matter of ours (Islam) will have it rejected. 
Birthday parties are an act of Bid’ah (innovation in religion) that should not be done for any person, regardless of their rank or role in life.
The most honorable of all creation and the best of all Messengers (peace be upon them), i.e. Muhammad ibn ‘Abdullah (peace be upon him) was never reported to have held a festival for the day he was born, or even instructed his Ummah (nation based on one creed) to celebrate it.
Similarly, the best of this Ummah after its Prophet (peace be upon him) are the Rightly-Guided Caliphs and the Sahabah (Companions of the Prophet), but none of them is reported to have made a festival for the Prophet’s birthday, or for any of them (may Allah be pleased with them), and all goodness is to be found in following their pathand patterning oneself after the teachings of the Prophet (peace be upon him).
Moreover, such Bid`ah pave the way to imitate the Jews, Christians and other Kafirs (non-Muslims) in terms of their newly invented festivals. Allah is the One sought for help!
May Allah grant us success! May peace and blessings be upon our Prophet Muhammad, his family, and Companions!
 Al-Bukhari, Sahih, Book on reconciliation, no. 2697; Muslim, Sahih, Book on judicial decisions, no. 1718; Abu Dawud, Sunan, Book on Al-Sunnah, no. 4606; Ibn Majah, Sunan, Introduction, no. 14; and Ahmad, Musnad, vol. 6, p. 240.
 Muslim, Sahih, Book on judicial decisions, no. 1718; and Ahmad Ibn Hanbal, Musnad, vol. 6, p. 180
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