There are enough evidences and references that supports Celebration of Mawlid an Nabi (sallalahualihiwasallam) . Mawlid continues to be celebrated from the days of prophet Alaihisalaatosalaam, Shaba (radiAllahuanhum), Ta'abayeen and Ta'abeTa'abayeen and untill today in various countries. Well as far as Biddah is concern, what we can say that there are various form of Biddah and celebration of Mawlid comes under the category of Biddah Hasanah ( Good Innovation) since Mawlid celebration is expression of joy and Happiness.

The Holy Qur’an Says ::..

قَالَ عِيسَى ابْنُ مَرْيَمَ اللَّهُمَّ رَبَّنَا أَنزِلْ عَلَيْنَا مَآئِدَةً مِّنَ السَّمَاءِ تَكُونُ لَنَا عِيداً لأَوَّلِنَا وَآخِرِنَا وَآيَةً مِّنكَ وَارْزُقْنَا وَأَنتَ خَيْرُ الرَّازِقِينَ

Eisa, the son of Maryam, said, “O Allah, O our Lord! Send down to us a table spread from heaven, so that it may become a day of celebration for us – for our former and latter people - and a sign from You; and give us sustenance - and You are the Best Provider Of Sustenance.” [Surah Al-Ma’idah, Verse 114]

The day when food is sent from skies is day of rejoicing (EID); then the day when soul of universe (Peace be with him) was born must be the delight for the day of rejoicing.

Look what Allah has said:

وَأَمَّا بِنِعْمَةِ رَبِّكَ فَحَدِّثْ

And abundantly proclaim the favours of your Lord. [Surah Al-Duha, Verse 11]

Allah himself commemorating Milad in Holy Qar’an as we do in our gatherings, Allah SubHanuhu wa Ta’ala Says in the Holy Qur’an:

هُوَ الَّذِي أَرْسَلَ رَسُولَهُ بِالْهُدَى وَدِينِ الْحَقِّ لِيُظْهِرَهُ عَلَى الدِّينِ كُلِّهِ وَكَفَى بِاللهِ شَهِيدًا

It is He Who has sent His Noble Messenger with the guidance and the true religion, in order to make it prevail over all other religions; and Allah is sufficient as a Witness. [Surah Al-Fatha, Verse 28]

وَإِذْ قَالَ عِيسَى ابْنُ مَرْيَمَ يَا بَنِي إِسْرَائِيلَ إِنِّي رَسُولُ اللهِ إِلَيْكُم مُّصَدِّقًا لِّمَا بَيْنَ يَدَيَّ مِنَ التَّوْرَاةِ وَمُبَشِّرًا بِرَسُولٍ يَأْتِي مِن بَعْدِي اسْمُهُ أَحْمَدُ فَلَمَّا جَاءَهُم بِالْبَيِّنَاتِ قَالُوا هَذَا سِحْرٌ مُّبِينٌ

And remember when Eisa the son of Maryam said, “O Descendants of Israel! Indeed I am Allah’s Noble Messenger towards you, confirming the Book Torah which was before me, and heralding glad tidings of the Noble Messenger who will come after me – his name is Ahmed (the Praised One)”; so when Ahmed came to them with clear proofs, they said, “This is an obvious magic.” [Surah As-Saf, Verse 6