Why did Allah not make a promise about guarding the hadiths, which are the secondary basic resource of Islam, as He made a promise about guarding the Quran?

Why did Allah not make a promise about guarding the hadiths, which are the secondary basic resource of Islam, as He made a promise about guarding the Quran? Can we say that all of the hadiths in the hadith books that reached us are definitely the words of the Prophet?

Dear Brother / Sister,

"We have, without doubt, sent down the Message; and We will assuredly guard it (from corruption)." (al-Hijr, 15/9)

It is a gleam of the miraculousness of the Quran that it is under the guardianship of Allah. That the words of the Prophet (pbuh) are not valued like the Quran is another sign of the divine identity of the Quran. Besides, the Prophet (pbuh) guarded the Quran by dictating it but he did not include his words in it. On the contrary, he did not allow hadiths to be written in the first years lest they should be mistaken for some words and expressions of the Quran.

Besides, we understand from the existence of fabricated narrations that it is possible to show some words that are not hadiths as hadiths. Hadiths are the resources that include the most eloquent expressions after the Quran but they do not have a distinction of being miracles. The attribute of miraculousness belongs to the Quran only. It is not appropriate in terms of justice and wisdom to equate the expressions of hadiths, which are not miracles, with the expressions of the Quran, which is a miracle. 

To sum up, that the Quran, one of the two resources that emerged in the hands of  Muhammad (pbuh), was guarded, that it was written with great care and recorded, that it has the tradition of being memorized by millions of hafizes and that it has been conveyed to us through a safe way is a clear indicator that the Quran is the word of Allah since it is not valid for hadiths, which are in the position of being the second resource.  The appearance of that miracle in a bright way necessitates the lack of any alternatives. This makes it necessary for the hadiths to be in a different position from the Quran.

On the other hand, hadiths and the Sunnah, which mean the life of the Prophet Muhammad (pbuh) and the living tafsir of the Quran, were guarded by the ummah, especially by his Companions. They were guarded by being practiced, written and memorized during the time of the Prophet and afterwards; they were applied and recorded in fiqh and hadith resources.

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