1. The Qur’an itself was not compiled into one uniform book during the Prophet's (ﷺ) time, so why is it’s compilation not considered a bid’ah?
2. The sanction of writing down and preserving hadith like Qur’an is not a bid’ah. In this context, why didn’t the Prophet (ﷺ) tell his companions to collect his statements since they were going to be used as secondary evidence with the Qur’an? Along the same lines, why weren’t the principles of fiqh, hadith, tafseer etc., not laid down during the lifetime of the Prophet (ﷺ) as these would become essentials in understanding and preserving the deen?
3. Dr. Bilal Phillps has said that something is also a bid’ah if the Prophet (ﷺ) had the means to do it but did not. The example he gave was drawing lines in the masjid and that the Prophet (ﷺ) could have done all these things in his lifetime. There may have not been a need to do so in his time, but Islam was not meant only for that time, it was meant for all of humanity till the Day of Judgment. Hence, how can we explain this relevant to today?
- The example of compiling the Qur'an into one book is similar to the example of praying Taraweeh in congregation or the additional adhan for Jumu'ah. These matters are not considered as bid'ah because they were introduced by the four rightly guided khulafa after the Prophet (ﷺ). And as the Prophet (ﷺ) said: “Follow my sunnah and the sunnah of the rightly guided khulafa after me. Bite on firmly to it with your molars. And beware of innovated matters, for every innovation is bid‘ah and every bid‘ah is misguidance.” 
So whatever was introduced by Abu Bakr, Umar, Uthman or Ali, comes in line with the Sunnah and is therefore not to be described as a bid'ah.
- As for the issue of why the various Islamic sciences were not compiled during the lifetime of the Prophet (ﷺ), then this in reality is a non-issue. There was no need to compile such sciences during that time because everyone understood the revelation without any need to refer to other studies to understand it. It was only when time passed and Islam reached the non-Arabs, that there was the need to introduce such sciences. Also, do not forget that the Prophet (ﷺ) was illiterate and he described his Ummah as an illiterate Ummah.
Furthermore, in order to understand the history of the compilation of the various Islamic sciences, you need to study that as a separate subject.
- Regarding the issue of placing lines in mosques for the prayer, I don't agree with the opinion that it is a bid'ah.
Please refer to:
(This is a complete fatwa that’s why I left the link as it is)
And Allah knows best.
 At-Tirmidhi 266, Abu Dawud 4607, Ibn Majah Vol. 1, Book 1, Hadith 42 and Musnad Ahmad< Back to Questions