Question: What is the ruling on preaching and giving sermons on the day of Mawlid (the Prophet’s birth)?
Answer: Propagation of virtue, prevention of vice, teaching people the rules of their religion, and admonishing them to soften their hearts are lawful at anytime, for the general stated commands to do so, without limiting any of them to specific times. Allaah (Exalted be He) says (what means): Let there arise out of you a group of people inviting to all that is good (Islaam), enjoining Al-Ma‘roof (i.e. Islaamic Monotheism and all that Islaam orders one to do) and forbidding Al-Munkar (polytheism and disbelief and all that Islaam has forbidden). And it is they who are the successful. Allaah (Glorified be He) also says… read more here.