الَّذِيۡنَ يَسۡتَمِعُوۡنَ الۡقَوۡلَ فَيَتَّبِعُوۡنَ اَحۡسَنَهٗ​ ؕ اُولٰٓـئِكَ الَّذِيۡنَ هَدٰٮهُمُ اللّٰهُ​ وَاُولٰٓـئِكَ هُمۡ اُولُوا الۡاَلۡبَابِ‏ 

 Who listen to speech and follow the best of it. Those are the ones Allah has guided, and those are people of understanding.

[Az-Zumer 39 :18]

Evidences from Qur'an:

1️⃣ First Evidence:

The Companions of our Prophet informed us that Allah had declared the following in the life of our Prophet صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم at the time of his last Hajj:

 الْيَوْمَ أَكْمَلْتُ لَكُمْ دِينَكُمْ وَأَتْمَمْتُ عَلَيْكُمْ نِعْمَتِي وَرَضِيتُ لَكُمُ الْإِسْلَامَ دِينًا

This day I have perfected for you your religion and completed My favor upon you and have approved for you Islam as religion.

[Al-Ma'idah 5:3]

2️⃣ Second Evidence:

   وَمَن يَبْتَغِ غَيْرَ الإِسْلاَمِ دِيناً فَلَنْ يُقْبَلَ مِنْهُ وَهُوَ فِي الآخِرَةِ مِنَ الْخَاسِرِينَ

And whoever desires other than Islam as religion – never will it be accepted from him, and he, in the Hereafter, will be among the losers.

[Ale 'Imran 3:85]

Allah Almighty has made it clear that inventing a new thing in our deen (religion) would not only be rejected but would also be punished heavily on the Day of Judgment.

Worst of all sins is inventing something new in our deen or Shari'a. Such additions are called bid'ahs and all bid'ahs lead to hell-fire.

Evidences from Hadith:

The Messenger of Allah صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم delivered a moving speech to us which made our eyes flow with tears and made our hearts melt. We said: "O Messenger of Allah صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم ! This is a speech of farewell. What do you enjoin upon us?"

He said: "I am leaving you upon a (path of) brightness whose night is like its day. No one will deviate from it after I am gone but one who is doomed. Whoever among you lives will see great conflict. I urge you to adhere to what you know of my Sunnah and the path of the Rightly-Guided Caliphs, and cling stubbornly to it. And you must obey, even if (your leader is) an Abyssinian leader. For the true believer is like a camel with a ring in its nose; wherever it is driven, it complies."

[Sunan Ibn Majah:43]

Rejection (in Deen) is of two kinds.

1⃣ Leaving out what has been prescribed by the Quran and Sunnah.

2⃣ Believing something to be a part of Deen which was not mentioned in Quran or by our Prophet  صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم .

12th Rabi ul Awwal… Birth date of our Prophet  صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم ?

12 th of Rabi ul Awwal is widely known as the birthday of our Prophet  صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم . However, historians have different opinions in this regard. Some consider 12th while others believe 9th of Rabi ul Awwal is the birthday of our Prophet  صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم .

The book "Rehmat ul lil Alameen":

A great book on seerah "Rehmat ul lil Alameen" was named as such because of the following ayah:

وَمَاۤ اَرۡسَلۡنٰكَ اِلَّا رَحۡمَةً لِّـلۡعٰلَمِيۡن

And We have not sent you, [O Muhammad], except as a mercy to the worlds.

[Al-Anbiya 21 :107]

The writer has truly presented our Prophet  صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم as "Mercy sent for all universe'.

Qadhi Allama Suleman has provided evidence that our Prophet  صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم  was born on 9th of Rabi ul Awwal, instead of the widely known 12th Rabi ul Awwal. 

If the date of birth of our Prophet صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم is not confirmed as 12th Rabi ul Awwal, how can we celebrate it as Eid Milad un Nabi? This is innovation in Deen, a bid’ah, which leads to Hell-fire.

According to most well known view, the date of death of our Prophet صَلَّى اللّٰهُ عَلَيْهِ وَسَلَّم is 12th Rabi ul Awwal. There seems to be no sense in celebrating the date of death of any person and that, too, with great pomp and joy.

Anything or any occasion, that was not mentioned in the Quran or in Sunnah and was not celebrated by the Sahabah is not worth celebrating. It is clearly a bid’ah, which should be avoided at all costs.