Ahmad ibn Yahyā al Winsharīsī رحمه الله narrated that al Ustādh Abū ‘Abdillah al Hafār al Mālikī (d.811) [1] was asked about the Mawlid, to which he replied,

“(celebrating) the night of the mawlid was not a reason for the Salif as Sālih (righteous predecessors), and they are the companions and the generation after them (tābi’een), to gather therein and engage in acts of worship, nor did they increase in doing anything which they did not do during other nights of the year.

This is because the Prophet صلى الله عليه وسلم is not honored except by means of what is legislated in the Shari’ah and deemed as being a means of honoring him since honoring him is from the greatest forms of worship bringing one closer to Allah.

However, a person does an action as a means of getting closer to Allah -the Most High- via what He has legislated.

The proof that the salaf did not do any type of additional worship during this night which they did not do during other nights is the fact that they differed with regards to when the Prophet صلى الله عليه وسلم was born.
It is said he صلى الله عليه وسلم was born in Ramadān. It is also said he صلى الله عليه وسلم was born in Rabī’ (al Awwal).

Likewise, with regards to the actual day he was born in, there are 4 opinions.

Thus, if the night of his birthday was connected to some sort of worship as a means of celebrating the birth of the best of creation صلى الله عليه وسلم it would have been well known and there would not exist a difference of opinion as to when it actually occured.

Consequently, no special type of worship is legislated as a form of honoring him on that day.

Do you not see that the day of al Jumu’ah is the greatest day wherein the sun has risen and the best action a person can do on a day that has some specific merit is to fast, yet the Prophet صلى الله عليه وسلم prohibited fasting on Jumu’ah with the specific intention of honoring that day.

As such, this is proof that no worship is done in a particular place or time, except that which has been legislated and what has not been legislated is not to be done. This is due to the fact that the later generations of this ummah cannot come with guidance that is superior to the first generations of this ummah.

If this door is open, then there would be those who say that the day he صلى الله عليه وسلم made hijrah to al Madīnah is a day wherein Allah honored Islām, and thus they would gather together to engage in certain types of worship.

Similarly, there would be another group of people who would say the night of al Isrā wherein the Prophet صلى الله عليه وسلم was taken up is a night that he صلى الله عليه وسلم was honored to such an extent that it is beyond comprehension so they would engage in some sort of worship.

Scenarios like these have no end.

However, all good is in following the salaf as sālih (the righteous predecessors) whom Allah choose to be with the Prophet صلى الله عليه وسلم. So what they did, we do, and what they left, we leave.

Finally, if this has been established, it is clear that gathering on the night of the mawlid is not something that is desired by the shari’ah.

[al Mi’yār al Mu’rab, v.7, pg.99-100]
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[1] He is Abu Abdillah Muhammad ibn ‘Ali known as al Hafār al Granādī who was the scholar of fiqh and hadīth in his area. He studied under ibn Lubb and had many students. From them, Ibn Sirāj and Abū Bakr ibn ‘Āsim.