Shaykh Uthman Dan Fodio stated:
If you were to say, “What is the legal judgment concerning what the people do during the month of Rabi` ‘l-Awwal on the day of Prophet’s birthday (al-mawlid) or on the seventh day of the mawlid where people gather together for remembrance of Allah (dhikr) and the food which is prepared for that purpose?” I say: That is a reprehensible innovation if it is free of every disobedience (ma`siyya). It is said that the answer is that the practice of the Mawlid of the noble Prophet, may Allah bless him and grant him peace is a highly recommended good innovation (bid`a hasana manduuba) when it is free of every disobedience. As for what the people have made a habit in these times where men and women mix freely, Allah forbid that any scholar would make that permissible.
It says in the al-Madkhal, “Generally what the people have invented from innovation is their false belief to be among the momentous acts of worship (akbar ‘l-`ibaadaat) and manifesting the rites of Islam is what they do during the month of Rabi` ‘l-Awwal from the Mawlid of the Prophet, may Allah bless him and grant hi peace. This has been included among the innovations (bid`a) and the forbidden things (muharramaat).” He continued, “It is necessary that when this noble month comes that it be honored, ennobled and respect it with deserving respect. This is by following the Prophet, may Allah bless him and grant him peace in that he used to single out times of blessing by increasing in performing acts of righteousness and generosity.”
If you were to say, “What is the legal judgment concerning those who prepare food only on the day of the mawlid. He intends by that the recognition of the mawlid and invites his Muslim brothers to eat along with that being free of every disobedience?” I say, This is a reprehensible innovation or an allowed innovation. The latter is the preferred decision (al-mukhtaar). The former decision was the opinion of the author of the al-Madkhal because he said, “If food is prepared only and one intends by that to recognize the Mawlid and the Muslim brothers are then invited even when it is free of every disobedience – it is still an innovation because of the intention only. This is because that is making increase in the religion and it is not among the behavior of the early community (as-Salaf). For following in the footsteps of the Salaf is paramount. No, rather it is obligatory.
Source: http://siiasi.org/wp-content/uploads/2011/10/ihyas-sunna-wa-ikhmadl-bida_2_.pdf (Ihya al-Sunna by Shaykh Uthman Dan Fodio, p. 189)