Answered by Shaykh Faraz Rabbani
Question: What is the concept of a “praiseworthy innovation” (bid`a hasana). How can an innovation be praiseworthy? Is the mawlid (celebration of the birth of the Prophet Muhammad) from this?
Answer: Walaikum assalam wa rahmatullahi wa barakatuh,
I pray this finds you in the best of health and spirits.
The concept of “praiseworthy innovation” (bid`a hasana) is basically a specific form of applying a general sunna of the Prophet (Allah bless him and give him peace), in a manner not contrary to the principles of Prophetic guidance.
Thus, for example, having an annual conference or religious event on specific dates (for reasons of practicality, without deeming this specification religiously-expected) is a specific way of applying the general sunna of spreading religious guidance.
The same applies to approved-of forms of group dhikr (which is considered permitted or praiseworthy by a large body of mainstream scholarship): the general sunna of group dhikr (understood from a large number of Prophetic hadiths) is being applied in a specific way.
And so on.
However, the scholars look carefully at the soundness of the basis for such actions; the component parts; and the implications of the action, direct and indirect.
Celebrating the Birth of the Prophet (peace and blessings be upon him)
In terms of the celebrating the Prophet’s birth, the basis of this is of two types: specific, from the sunna itself: the Prophet (Allah bless him and give him peace) celebrated the day of the week in which he was born by fasting on Mondays–so why would celebrating the date of his birth, in permitted & sound ways, be wrong?  general, from the call in the Qur’an and Sunna to express thankfulness and rejoicing in the blessing and gift from Allah that is our Beloved Messenger of Allah (peace & blessings be upon him & his folk).
Again, if we follow the recourse that Allah Most High has given us: returning matters we’re not clear of to the people of knowledge, then we see that the mawlid, for example, has been carefully considered and generally approved of right across the four schools of mainstream Islamic law.
If someone doesn’t feel comfortable with that, it is fine, but condemning a mainstream action approved by mainstream Islamic scholarship is the basis of division, and contrary to established principles. “There is no condemnation in matters of genuine difference.” (la inkara fi masa’il al-khilaf)
And Allah alone gives success.